Jc Is THE THREE KINGDOMS OF NATURE, &c. &c. THE THREE KINGDOMS OF NATURE BRIEFLY DESCRIBED. REV. S. HAUGHTON, F.R.S., M.D.DuBL., D.C.L.Oxox., FELLOW OF TRINITY COLLEGE, DUBLIN. WITH TWO HUNDRED AND THIRTY ILLUSTRATIONS, Drawn on wood and engraved by G. A. HANLON. LONDON : CASSELL, PETTER, AND GALPIN, AND 596, BROADWAY, NEW TOEK. [All Rights Reserved.] DUBLIN : }p vintet) .it BY M. H. GILL. PREFACE THE faculties of our minds are developed in succession, as we advance in age, each of them reaching its maximum, and then gradually diminishing. In childhood, the senses acquire their greatest developement ; in boyhood and youth, the memory and imagination ; in early manhood the purely reasoning faculties ; and in adult life, the judge- ment. A rational system of education should be guided by the physiological law here laid down. The child should be instructed mainly through his sensations ; the boy should learn Languages, ancient and modern, and Natural History, so far as it depends on observation ; the youth should cultivate Mathematics and Logics ; while studies, such as Ethics, Physiology, and Politics, should be re- served for the more mature period of life, in which the judgement corrects the rash conclusions founded on mere memory and reason. Considered from the foregoing point of view, the ne- glect of Natural History, as a school study, appears most unaccountable, as it is inferior to no other study not even Language as a means of cultivating the memory and observation. 2091 Of, 1 VI PREFACE. One cause of this neglect is certainly the want of suit- able books, and of teachers. An attempt is made in the following pages to supply one of these wants by means of a small book, adapted for school and self-instruction ; and care has been taken to present the Three Kingdoms of Nature to the learner, with a due regard to their relative importance. The Author takes this opportunity of thanking the Provost and Senior Fellows of Trinity College for their liberality in defraying the entire cost of the numerous woodcuts with which the book is illustrated. TRINITY COLLEGE, DUBLIN, December 24, 1868. CONTENTS. PART I. THE MINERAL KINGDOM. CHAPTER I. CRYSTALLOGRAPHY. PAGE. 1. The Monometric System, 3 2. The Dimetric System, ........ 14 3. The Trimetric System, . 17 4. The Monoclinic, Diclioic, and Triclinic Systems, . . . 19 5. The Hexagonal System, 21 CHAPTER II. COMPOSITION OF MINERALS. Classification of Minerals, ....... 26 The Simple Oxides, 29 A. The Quartz Family, 29 (o.) Amethyst, 29 (.) Chalcedony, ........ 29 (c.) Agate, 29 (d.) Jasper, 30 (e.) Flint, , 30 C/-) Opal, 30 B. Corundum, 30 C. Iron Oxides, 31 (a.) Red Haematite, ....... 31 (5.) Brown Haematite, 31 D. Manganese Oxides, 31 viii CONTENTS. PAGE. E. Copper Oxides, .... 32 (.) Ked Copper Ore, ... 32 (5.) Black Copper Ore, . 32 F. Tinstone, 3 2 G. Titanium Oxide, 33 (a.) Eutile, ..... 34 (#.) Anatase, 34 (c.) Brookite, 34 3. The Compound Oxides, 34 A. Spinelle, 34 B. Magnetic Iron Ore, 35 4. The Silicates, 35 5. The Felspar Family, ... 35 A. Orthoclase, 36 (a.) Adularia, 37 (*.) Sanidine, 37 (w.) Follicle, ....... j ,5 (.) Legume, ........ I5 6 (o.) Loment, ....... .156 (p.) Capsule, ........ I g (r.) Silique, .... ..... I5? () Silicle ......... 157 (<.) Cone, . ........ I57 (.) Galhalus, ........ T ,- CHAPTER IV. THE LIFE OF PLANTS. 1. Circulation of the Sap, ........ jro 2. Respiration of Plants, ........ l ( > , 3. Nutrition of Plants, ........ xg- 4. Reproduction of Plants, . . . .. . . . ^ A. Vegetative Multiplication, ...... I7r B. True Reproduction, ....... j.,, (fl.) Flowering Plants, ...... !-j (b.) Flowerless Plants, ...... I7 xvi CONTENTS. CHAPTER V. THE CLASSIFICATION OF PLANTS. 1 . Classification of Linnaeus, ..... 2. Natural Classification of Plants, .... A. System of Jussieu, ...... B. System of De Candolle, PART III. THE ANIMAL KINGDOM. CHAPTER VI. VERTEBRATE ANIMALS. 1. Classification, . . . . . . . . . 185 2. Mammals, ......... 190 A. Skeleton, 191 B. Nervous System, . . . . . . . 195 (a.) Cerebrospinal, . . . . . . . 195 (i.) Sympathetic, 197 C. Respiration, ........ 198 D. Circulation, . . . . . . . . 199 E. Digestion, ........ 202 (a.) Mouth, ........ 203 (b.) Pharynx and (Esophagus, ..... 203 (c.) Stomach, ....... 204 (rf.) Duodenum, ....... 206 (e.) t Small intestines, ...... 207 (/.) Caecum, ........ 207 (^.) Colon and Rectum, ...... 208 F. Liver and Kidneys, ...... 208 3. Classification of Mammals, . . . . . . 211 A. Man, . . . . . .. . . 212 B. Quadrumans, . . . . . . . . 212 (a.) Strepsirhine, . . . . . . . 213 (6.) Platyrhine, . . . . . . . 214 (c.) Catarrhine, . . . . . . . 214 CONTENTS. FAOK. C. Cheiropters, 215 D. Carnivores, .... ... 216 (a.) Digitigrade, . . . . . . 217 (i.) Plantigrade, 220 (c.) Pinnigrade, . . . . . . . 221 E. Insectivores, . . . . . . . . 222 F. Ungulates, 224 (a.) Even-toed, ....... 224 1. Ruminants, ....... 224 2. Omnivores, ....... 230 (*.) Odd-toed, 231 1. Solidungulates, ...... 232 2. Multungulates, ...... 233 3. Proboscidians, . . . . . . 234 G. Rodents, ........ 235 H. Cetaceans, ........ 238 (a.) Carnivorous, . . . . . . . 238 (b.~) Herbivorous, . . . . . . . 240 I. Edentates, ........ 241 (a.) Burrowing, . . . . . . . 241 (i.) Tardigrade, . . . . . . . 242 K. Marsupials, ........ 243 L. Monotremes, . ...... 246 Birds, .......... 247 A. Skeleton, ........ 247 B. Nervous System, ....... 249 C. Respiration, . . . . . . . . 249 D. Circulation, ........ 250 E. Digestion, . . . . . . . . 251 F. Liver, Pancreas, and Kidney, . . . . . 252 Classification of Birds, ....... 252 A. Raptorial, ........ 253 B. Passerine, ........ 253 (a.) Dentirostres, ....... 254 (#.) Fissirostres, ....... 254 (c.) Conirostres, ....... 254 (d.~) Tenuirostres, ....... 255 (e.) Syndactylae, ....... 155 C. Climbing, . ... 255 xviii CONTENTS. PAGE. D. Gallinaceous, .... .... 256 E. Running, 256 F. Wading, ... 257 (a.) Pressirostres, 258 (5.) Cultrirostres, . 258 (c.) Longirostres, ... .... 258 (d.~) Macrodactylae, 258 G. Swimming, .... .... 259 (a.) Brevipennes, . . . . 259 (6.) Lamellirostres, .... . . 259 (c.) Totipalmatse, ... .... 260 (rf.) Longipennes, 260 6. Reptiles, .... 260 A. Skeleton, 260 B. Nervous System, 262 C. Respiration, 262 D. Circulation, 263 E. Digestion, 264 F. The Liver, Pancreas, and Kidneys, 265 7. Classification of Reptiles, . 266 A. Amphibians, 266 (a.) Ophidobatrachian, 266 (i.) Saurohatrachian, 267 (c.) Chelonobatrachian, 269 B. True Reptiles, 269 (a.) Serpents, 270 (5.) Lizards, 272 (c.) Tortoises, 276 8. Fishes, 278 A. Skeleton, 279 B. Nervous System, . . . . . . . . 280 C. Respiration, 280 D. Circulation, 280 E. Digestion, 282 F. Liver and Kidneys, ....... 282 9. Classification of Fishes, 283 A. Septocardians, . . . . . . . . 283 B. Cyclostomes, . 284 C. Sirenoids, ...... ... 285 CONTENTS, xix D. Placoids, 286 E. Ganoids, ......... 287 F. Teleosteans, 288 CHAPTER VII. INVERTEBRATE ANIMALS. 1. Articulates, 292 2. Classification of Articulates, . . . . . . 294 A. Insects, ......... 295 (a.) Apters, . . . . . . . . 298 (b.) Strepsipters, ....... 300 (c.) Dipters, ...... 301 (<) Hymenopters, ....... 302 (e.) Lepidopters, ....... 308 (/.) Neuropters, . . . . . . 310 (g.) Hemipters, ....... 313 (A.) Orthopters, . . . . . . . 317 (t.) Coleopters, . . . . . . . 319 B. Myriapods, . . . . . . . . 323 (.) Centipedes, . . . . . . . 323 (b.} Millipedes, ....... 324 C. Arachnids, ... .... 325 (a.) Spiders, ..... . . 325 (5.) Scorpions, ..... . 326 (c.) Mites, ........ 327 (d.~) Sea Spiders, ....... 327 D. Crustaceans, ........ 327 (a.) Stalk-eyed, 328 1. Decapods, ....... 328 2. Stomapods, ....... 329 (t>.) Sessile-eyed, . . . . . . . 330 1. Amphipods, ....... 330 2. Isopods, . . . . . . . 331 (e.} Entomostracans, ...... 332 (d.) Cirripedes, . . . . . . . 335 (e.) Xiphurids, . . . . . ' . . 336 E. Annelids, ........ 337 (.) Sucking worms, ...... 339 (6.) Bristle-bearing worms, ..... 340 (e.) Sipunculids, . . . . . 343 xx CONTENTS. PAGE. F. Scolecids, 343 O.) Rotifers, -344 (5.) Turbellarians, 347 (c.) Trematodes, ....... 348 (rf.) Cestodea, 34 8 (.) Nematodea, ....... 349 (/.) Acanthocephalids, ...... 350 (g.) Gordians, . . . ... . 350 3. MoUusks, -351 4. Classification of Mollusks, . . . . . . 352 A. Cephalopoda, ... .... 352 (a.) Dibranchiate, . . . - . . . 353 (a.) Octapods, 354 (/3.) Decapods, 356 (i.) Tetrabrancbiate, 358 B. Pteropods, 358 C. Gasteropoda, ........ 359 (a.) Prosobrancbiate, . . . . . . 359 (J.) Pulmobranchiate, ...... 362 (c.) Opistbobranchiate, ...... 363 (rf.) Heteropods, . . . . . . . 364 D. Lamellibranchs, . . . . . . . 365 E. Brachiopods, ........ 368 F. Ascidians, ........ 369 G. Polyzoans, ........ 370 5. Radiates, ......... 371 A. Echinoderms, . . ...... 372 (a.) Crinoids, ....... 374 (5.) Asteroids, ....... 375 (c.) Ecbinoids, ....... 376 (rf.) Holothuroids, . . . . . . 377 B. Ccelenterates, . . . . . . . . 377 (a.) Actinozoan, . . . . . . . 378 (.) Hydrozoan, . . . .*.... . . 381 6. Protozoans, ......... 383 A. Rbizopods, ........ 384 B. Sponges, 385 C. Gregarines, ........ 386 D. Infusories, ........ 387 ELEMENTS OF NATURAL HISTORY PART I. THE MINEEAL KINGDOM. "LAPIDES Corpora congests, nee viva nee sentientia." " Regnum Lapideum rude inhabitat interiora ; a salibus in terris gene- ratur ; temere miscetur ; casu modificatur." Linnaus. CHAPTEE I. CRYSTALLOGRAPHY. A MINERAL is an inorganic substance formed in the earth, pos- sessing a definite geometrical shape, and a definite chemical composition. Rocks and stones are formed of minerals, some- times quite pure, hut more frequently mixed together in various proportions, from mechanical causes ; minerals are the result of the chemical union of different bodies, while rocks, for the most part, are the product of various physical causes ; hence the study of Mineralogy must precede that of Physical Geology, which ex- plains the mode of production of the various rock masses of which the surface of the globe is composed. Let us take for example a piece of calc spar, and a piece of slate ; the calc spar is called a mineral, because it is generally 2 ELEMENTS OF NATURAL HISTORY. found crystallized in certain definite shapes, and never in any others, and to have the following definite chemical composition : Carbonic Acid, 44 per cent. Lime, 56 The piece of slate, on the other hand, although it presents a certain structure called cleavage, by reason of which it can readily be split into thin plates, shows no tendency to assume any defi- nite crystalline shape; and although, on chemical analysis, it may be found to have a definite composition, through large tracts of country, yet this is found to be the result of the homogeneity of the fine mud of which it was originally composed, by mecha- nical deposition from water, and is in no respect due to the definite results of chemical combinations. Thus, the average compo- sition of roofing slate may be Silica, 60.5 per cent. Alumina, 19.7 Protoxide of Iron, 7.8 Lime, ....'.. i.r Magnesia, 2.2 Potash, 3.2 Soda, 2.2 Water, 3.3 Each of the constituents here named, silica, alumina, &c., are themselves the result of definite chemical combinations, and some of them are minerals found in nature ; yet they are not combined together in a definite manner to form the compound called roofing slate ; they are present as constituents of several minerals quite distinct from each other, but which happen, in the case considered, to be mixed up accidentally in various proportions by the mecha- nical action of running water, which has deposited the whole mixture originally in the form of fine mud. CE YS TALLO GRA PHY. The first subject to be considered in Mineralogy is, therefore, the geometrical forms of minerals, and this branch of the subject is generally called Crystallography. Crystals are geometrical solids, bounded by planes, which are related to each other by definite laws that are never departed from. All the crystals found in natural or artificial compounds are reducible to the following seven groups, which are called crystalline systems : 1. The Monometric system. 2. The Dimetric system. 3. The Trimetric system. 4. The Monoclinic system. 5. The Diclinic system. 6. The Triclinic system. 7. The Hexagonal system. These systems are classified as follows : i. Monometric three axes equal. A. Referred to three axes making right angles with each other. B. Referred to three axes making one or more acute angles with < each other. 2. Limetric two axes equal. 3. Trimetric axes unequal. 4. Monoclinic one acute angle be- tween axes. 5. Diclinic two acute angles be- tween axes. 6. Triclinic three acute angles be- tween axes. C. Referred to the three diameters of a regular hexagon, and to a fourth axis drawn at their 7. Hexagonal. point of intersection, perpen- dicular to their plane. i. The Monometric System. It is proved by Euclid (xiii., 1 8, Scholium), that there are five solids, and five only, whose faces make equal angles with each other, and are bounded by regular figures. These are called the Eegular Solids, and are all inscrib- able in a sphere. Their names are B 2 4 ELEMENTS OF NATURAL HISTORY. 1. The Tetrahedron, or Four- faced Solid; 2. The Hexahedron, or Six- faced Solid; 3. The Octahedron, or Eight-faced Solid ; 4. The Dodecahedron, or Twelve-faced Solid ; 5. The Icosahedron, or Twenty-faced Solid. The Tetrahedron, or Pyramid (Fig. i.) has equilateral tri- angles for its faces, and is bounded by four such faces. The Fig. i. Tetrahedron has six edges, which make with each other the angles of an equilateral triangle. Fig. 2. The Hexahedron, or Cube (Fig. 2), has squares for its faces, E UCL IDEA N SOL IDS. 5 and is bounded by six such faces. It has twelve edges which make right angles with each other. The edges of the cube are parallel to the three monometric axes; and the relation between the Cube and Tetrahedron is best shown by means of (Fig. 3), which gives the construction of Euclid (xv., i.) " To inscribe a Pyramid in a given Cube." If the diameters of the cube were drawn aa', bb', cc' ; they would pierce the faces Fig- 3- of the pyramid at right angles, and pass through their centres of gravity. The diameters of the cube are four in number, and are called the Tetrahedric axes, because they are perpen- dicular to the four faces of the inscribed tetrahedron. They are sometimes called the Octahedric axes, because they are also per- pendicular to the faces of the inscribed octahedron. The edges of the cube are called the Cubical, or monometric axes ; and if they be assumed equal to unity, then the Tetrahe- dric axes, or diameters of the cube will be each represented by The tetrahedric axes make each three angles with the 6 ELEMENTS OF NATURAL HISTORY. cubical axes, which are equal to each other, and to 70 32' nearly.* The Octahedron (Fig. 4) has equilateral triangles for its faces, and is bounded by eight such faces ; it has twelve edges, Fig. 4. which make angles with each other equal to those of an equi- lateral triangle, or of a square. b Fig- 5- The relation between the Cube and the Octahedron is shown in Fig. 5, which gives the construction of Euclid (xv. 3.) * The exact angle is given by the relation Secant = v/3- EUCLID EA N SOL IDS. 7 " To inscribe an Octahedron in a given Cube." The four diameters of the cube aa, bb f , cc, dd f , pierce the faces of the oc- tahedron at right angles, and pass through their centres of gravity. The propriety of the term octahedric axes is apparent from the construction. The Pentagonal Dodecahedron, Fig. 6, has regular pentagons for its faces, and is bounded by twelve such faces ; and has thirty edges, which make with each other the angles of a regular pen- tagon. The Tetrahedron, the Cube, and the Octahedron, are found repeatedly in the mineral kingdom, and are combined with each other in infinite varieties ; but it is remarkable that the Pentago- nal Dodecahedron has not yet been discovered in the mineral kingdom, although some of its combinations with the other regu- lar solids are well known. In like manner, the Icosahedron, or twenty-faced figure, has not yet been found, except in combi- nation with the Octahedron. The Pentagonal Dodecahedron is met with in the solids formed by the mutual pressure of the cells of plants, and half the dodecahedron is known to occur in the cup-shaped calyces of some of the fossil Stone Lilies. ELEMENTS OF NATURAL HISTORY. The Icosahedron, or twenty-faced figure, Fig. 7, has equila- teral triangles for its faces, and is bounded by twenty such ; it has thirty edges, which make with each other the angles of the equilateral triangle or of the pentagon. Like the Dodeca- hedron, it occurs in minerals, only in combination with the other regular solids, and never simply by itself. All the crystals of the Monometric system are either Fig. 7. the result of the superposition of the Euclidean solids, or of simple combinations formed by building pyramids of regular form upon their faces. One of the most interesting of the forms resulting from su- perposition, is the Cubo-Octahedron, Fig. 8, so called because it is the combination of the Cube and Octahedron in which neither solid predominates. The Cubo- Octahedron is bounded by six squares and eight equilate- ral triangles ; it has twenty-four edges, which, like those of the Euclidean solids, are all equal to each other, and these edges make with each other angles which are Fig. 8. equal to those of the equilateral triangle, the square, or the regular hexagon. The Pyramidal modifications of the Euclidean solids are formed by building regular pyramids upon the faces of the pri- mary solid ; and by comparing different forms of these solids with pyramids built upon their faces, several very interesting THREE-FACED OCTAHEDRON. relations between them become apparent, which could not other- wise have been perceived. The Pyramidal Cube is shown in Fig. 9, and is formed by constructing four-faced pyramids upon the six faces of the primary Cube. The Pyramidal, or Three-faced Octa- hedron, is shown in Fig. 10, and is formed by building up regular three- faced pyramids upon the eight faces of the primary Octahedron. When the Pyrami- Fig. 9 . dal Cube and Pyramidal Octahedron are compared with each other, they are to be supposed as placed in the relative positions shown in Fig. 5, in which the Octahe- dron is represented as inscribed in the cube. The number of faces in the Pyramidal Cube is found from the consideration that each of the four-faced pyramids, p, q, r, &c., is built upon one of the six faces of the primary cube, and hence the total number of faces of the pyramidal cube is 6 x 4 = 24. In like manner, in the Pyramidal Octahedron, since each of the three-faced pyramids, p, q, r, , &c., is built upon one of the eight faces of the primary Octahedron, the total number of faces must be 3 x 8 = 24. If the pyramids p, q, r, &c., in the Cube, or the pyramids p, q, r, s, &c., in the Octahedron, were so constructed that the planes joining the vertices p, q of the pyramids with the intervening edge, ab, of the primary solid were to coincide, we Fig. 10. ELEMENTS OF NATURAL HISTORY. should have thus produced a remarkable solid, having twelve faces, each of which would be a rhombus, the ratio of whose diameters is Y/2 : i, or in the proportion of the diameter to the side of a square, and which is well known to mineralogists and naturalists under the name of the Rhombic Dodecahedron. The Rhombic Dodecahedron is shown in Fig. 1 1 , inscribed in the cube abed, whose edges are bisected in the points C, B, G, D, E, F, and the lines CC', ', GG, DD', EE', &c. (six in number), drawn to join the points of bisection of the opposite edges of the faces of the c ube, are perpendicular to the faces of the inscribed Rhom- bic Dodecahedron, and are thence called Dodecahedral Axes of the Cube. The diameters of the cube, aa' bb 1 , cc', dd' (four in number), drawn to join the opposite angles of the Fig. ii. cube, pass through the trihedral angles of the Rhombic Dodecahe- dron, and, as already shown, are perpendicular to the faces of the inscribed octahedron and tetrahedron, being the tetrahedric or octahedric axes of the cube. The Rhombic Dodecahedron forms the connecting link between the pyramidal cubes and octahedrons, just as the Cubo-octa- hedron forms the connecting link between the cube and octa- hedron. Its edges are all equal to each other, and its faces make equal angles, each angle being (120) that of a regular hexagon. It occurs frequently in the mineral kingdom, and is well known to naturalists as the form assumed by the cell of the working bee, which is instructed to form it by a skill su- perior to its own. SIX-FA CED OCTA HEDRO A". Fig. 1 2. If regular pyramids be built upon the faces of the Tetra- hedron we obtain the Pyramidal, or three- faced Tetrahedron, shown in Fig. 12. The pyramidal cubes, octahe- drons, and tetrahedrons have faces formed of isosceles triangles, whose bases form the edges of the pri- mary solid from which they are derived, and they may readily be recognized by this property. There is another class of modifications of the primary forms of Cube, Octahedron, and Te- trahedron, whose faces are formed of scalene triangles. These are known by the names, Six - faced Octahe- dron, Eight- faced Cube, and Six-faced Tetrahedron. The Six -faced Octahedron, or Eight- faced Cube is shown in Fig. 1 3, in which it is easy to recognize the primary forms both of the Cube and Fig- 1 3- Octahedron, masked by the modifying planes. The Six-faced Tetrahedron is shown in Fig. 14, in which only one face is drawn, to prevent confusion in the figure. A Deltoid is known in Geometry as a figure formed by two unequal isosceles triangles, constructed on opposite sides of the same base. There are two remarkable forms of crystals whose faces are Deltoids, and which are to be regarded as modifications of the Tetrahedron and Octahedron respectively. If, having constructed pyramids, as shown in Fig. 1 2, upon ELEMENTS OF NATURAL HISTORY. the faces of a Tetrahedron, we turn each of these pyramids round its axis, so that each face shall occupy a position halfway between the original faces of the pyramid the faces of the pyramids inter- secting each other will form a twelve-faced solid, shown in Fig. 1 5, whose faces are deltoids, the longer sides of which cor- respond to the original edges of the primary Tetrahedron. This figure is known to crystallographers as the Deltoid Dodecahedron, or Deltoidal Te- trahedron. If the same construction be Fig. 14. performed upon the pyramidal octahedron, Fig. 10, another solid is produced, which is bounded by 24 deltoidal faces, and is called the Deltoidal Octahedron. It is of frequent occurrence in the mineral kingdom, and is shown in Fig. 16. It would be impossible to give an adequate idea, in an ele- mentary treatise, of the innu- merable variety of forms of crys- tals produced by the combina- tions of these elementary forms with each other, and the foregoing are selected as the most inte- resting of their class, because their faces are bounded by the simplest plane figures ; squares, rhomboids, equilateral and isosceles triangles, or scalene triangles, symmetrically placed, and deltoids. It may help the remembrance of these different crystallogra- phical forms to associate them with the names of well-known mi- Fig. 15- THE DELTOID SOLIDS. nerals which frequently assume them. This is done in the fol- lowing table, which might readily be extended : Fig. 1 6. Crystalline Form. i. Tetrahedron, . . . ii. Cube, Mineral. Grey Copper Ore, or Fahlerz. / i. Fluor Spar. 2. Galena. 3. Rock Salt. 4. Iron Pyrites. \. Alum. u. Spinelle. Galena. v. Pyramidal Cube, .... C: Native Copper. Native Gold. {I. Galena. vi. Pyramidal Octahedron, . . , Diamond. vn. Rhombic Dodecahedron, . . Garnet. vin. Pyramidal Tetrahedron, . . Grey Copper Ore. ix. Six-faced Octahedron, or f * Diamond. Eight-faced Cube, . . . U Garnet. x. Six-faced Tetrahedron, . . Diamond. xi. Deltoidal Tetrahedron, . . Grey Copper Ore, . j Analcime. xn. Deltoidal Octahedron, . . . 2. Leucite. ELEMENTS OF NATURAL HISTORY. Fig. 17. 2. The Dimetric System. In this Crystalline system, as in the Monometric and Trimetric systems, the axes of the crystal con- sist of three lines at right angles to each other, the portions measured off on the three axes in the Dimetric system being two equal and one unequal. In the monometric system, as all the axes were equal, it was a matter of in- difference how the crystal was placed for study ; but in the present instance one axis is unique, and is, therefore, placed vertically in examining the crystal. In Fig. 17 is shown the typical form of the dimetric system ; its unequal axis is placed vertically, and is the axis of a right square prism, surmounted at each extremity by a half octahedron, the axis of which corresponds with the unequal axis of the system. In the first system no reference is made to the lengths of the three axes, for they are all equal, and may be taken as unity. In the Dimetric system it is necessary to state the ratio of the un- equal to the two equal axes ; and this ratio is called the parameter of the Dimetric system. If, in Fig. 1 7, we suppose the square prism to remain fixed, while the octahedron is turned round on its axis through half a right angle, we shall ob- tain the combination shown in Fig. 18. If the prism be turned through half a right angle, while the octahedron remains fixed, we shall obtain the combination shown in Fig. 19. And, finally, if two complete crys- tals, as in Fig. 17, composed of square prisms, with their half octahedrons at- tached, be superposed on each other, so as to allow a bevelment of the edges to take place, we shall obtain the form shown in Fig. 20, which is of frequent occurrence in the Dimetric system. Fig. 18. THE D I METRIC SYSTEM. The octahedron of the Dimetric system has isosceles triangles for its faces, and the vertical angles of the isosceles triangles are Fig. 19. greater or less than the angles of an equilateral triangle, accord- ing as the vertex of the dimetric octahe- dron falls below or above the vertex of the regular octahedron of Euclid. The edges of the octahedron are of two kinds eight terminal edges formed by the sides of the isosceles triangles, and four lateral edges, which form a square, and are the bases of the isosceles triangles. In the Monometric system there was only one octahedron, that of Euclid, which is inscribable in a sphere ; in the Dimetric system there are an innumerable number of octahedrons, each with a square base, but differing from each other in the height of the vertex. It is found, however, that these octahedrons are related to each other in a very simple manner. If p denote the parameter of the octahedron with the lowest vertex, its faces cut off lines on the three axes, which are respec- tively equal to I : i : p i6 ELEMENTS OF NATURAL HISTORY. and the diameters of this primary octahedron are double the pre- ceding numbers, viz. : 2 : 2 : zp It has been found that all the secondary octahedrons of the Dimetric system, when placed upon the same square as base, have their vertices always at a height that is double, triple, quadruple, &c., the height of the vertex of the primary octa- hedron. In general, therefore, we have the faces of the different octahedrons denoted as follows : First Octahedron, Second Octahedron, Third Octahedron, m th Octahedron, ...... The combinations of the primary and secondary octahedrons with each other produce very elegant forms. One that frequently occurs is shown in Fig. 21, which shows the com- bination of a dimetric octahedron with two other dimetric octahedrons one of which is less acute than itself, but symmetrically placed; while the other is more acute, and has been turned round through half a right angle previous to combination. The following minerals furnish good examples of the Dimetric system of crystals : 1. Tinstone. 2. Entile. 3. Anatase. 4. Zircon. 5. Idocrase. 6. Apophyllite. 3P i : i : mp Fig. 21. THE TRIMETRIC SYSTEM. 3. The Trimetric System. In this system, the axes, as be- fore, are at right angles with each other, hut their lengths are all unequal, so that there are two parameters in the system which express the ratios of the second and third axes, respectively, to the first. The accompanying Fig. 22 shows the primary octahedron of the Trimetric system inscribed in its primary prism. Its axes aa', W, cc', are equal to the edges of the prism, and intersect at right angles. The octahedron of the Trimetric system has, there- fore, scalene triangles for its faces, and is constructed upon rhombic bases. Secondary octa- hedrons are met with in this sys- tem as well as in the Dimetric system. If p and q denote the parameters of the system, or ratios of the second and third axes to the first; the primary Fig- 22 - octahedron cuts off lengths on the axes equal to 1 : p : q and its diameters are 2 : ip : iq In the Dimetric system, the secondary octahedrons were formed by taking integer multiples of the unique axis, and therefore only one set of secondary octahedrons existed : in the Trimetric sys- tem we may take integer multiples of any of the three axes, and use them to construct secondary octahedrons ; we may therefore have any of the following octahedrons in combination with the primary or with each other : m : p i : mp i : p mp C 1 q mq nq 18 ELEMENTS OF NATURAL HISTORY. In nature, very few secondary octahedrons are met with except the following : Primary, i : p : q Secondary, i : p : iq * = P 3? 2 : zp : q 3 = 3P 9 The most common of all the combinations in the Trimetric system is that of the primary octahedron and prism. Such a combination is shown in Fig. 23, in which the summits of the octahedron are sliced off by the faces of the prism, and re- placed by rhombic faces. Fig- 23- The primary prism, with its inscribed primary octahedron, is shown in Fig. 22 but there are secondary prisms corres- ponding to each secondary octahedron, formed by taking mul- Fig 24. Fig. 25. tiples of the axes along the diameters a,b,c. These prisms, when combined with each other, or with the various octahedrons, give THE CLINIC SYSTEMS, 1 9 rise to many elegant forms of crystals. In Fig. 24 is shown the combination of two prisms parallel to one axis, with two prisms parallel to another axis ; those of the third axis being absent. In Fig. 25 is shown a combination of two octahedrons, pri- mary and secondary, with terminal planes and a prism. The ter- minal planes slice the summits off both the octahedrons; and the prism bevels four of the edges of the primary octahedron. The number of combinations possible from the union of the various octahedrons and prisms in the Trimetric system is very great, but they are easily recognized after a little practice, in consequence of the great symmetry of the system referred to its rectangular axes. The following minerals furnish good examples of the Trimetric system of crystals : 1. Aragonite. 2. Harmotome. 3. Stilbite. 4. Topaz. 5. Sulphate of Barytes (Heavy Spar). 4. The Monoclinic, Diclinic, and Triclinic Systems. The Clinic systems differ from the Metric systems, in Crystallography, in this respect, that their axes contain one or more acute angles, while those of the Metric systems are always at right angles to each other. Thus, in the Metric systems, the greatest number of constants necessary to define the crystal is only two, viz., the parameters that express the ratios of the lengths of two of the axes to the third ; but, in the Clinic systems, the number of constants ranges from three to five, in the following manner: 1 . Monoclinic System Contains two parameters, and one acute angle. 2. Diclinic System Contains two parameters, and two acute angles. 3. Triclinic System Contains two parameters, and three acute angles. c 2 20 ELEMENTS OF NATURAL HISTOEY. In Fig. 26 I have shown the octahedron of the Clinic systems, inscribed in the prism of the same systems. The ratios of the axes aa', bb', cc f , to each other are, as hefore, the parameters of Fig. 26. the system ; and it is Monoclinic, Diclinic, or Triclinic, according as one, two, or three, of the angles made with each other, by aa', bb', cc', are acute and not right. There are secondary octahedrons and secondary prisms in the Clinic systems that modify each other, and produce combi- nations analogous to those described in the Trimetric system, but much more complex, and subjected to laws too difficult for examination in an elementary treatise. The following minerals and salts afford examples of the crys- tals belonging to the Clinic systems : Monoclinic. 1. Realgar (Sulphuret of Arsenic). 6. Felspar. 2. Carbonate of Soda. 7. Sphene. 3. Wolfram. 8. Gypsum (Sulphate of Lime). 4. Epidote. 9. Sulphate of Iron. 5. Augite. THE HEXAGONAL SYSTEM. 21 Diclinic. Naumann has discovered a Clinic system with only one right angle in certain artificial salts, and some crystallographers sup- pose that Felspar may be referred to this system. Triclinic. 1. Labradorite. 2. Albite. 3. Anorthite. 4. Axinite. 5. Sulphate of Copper. 5. The Hexagonal System. This system is referred to a re- gular hexagon as base, and its primary forms are the Hexagonal Dodecahedron, Fig. 27, and the Hex- agonal Prism Fig. 28, which may be terminated by the Hexagonal Dodeca- hedron, or by flat summits. The form Fig. 27. Fig. 28. shown in Fig. 27 is often assumed by the mineral called Gme- lenite, and Fig. 28 is a common form of Quartz : the flat ter- minations of the hexagonal prism are best shown by Apatite and Emerald. The Hexagonal Dodecahedron has twelve faces, eighteen edges, and eight angles ; the faces are isosceles triangles, and the edges are of two kinds twelve terminal, forming the sides of the tri- angles; and six lateral, forming the bases of the same triangles. ELEMENTS OF NATURAL HISTORY. If the hexagonal dodecahedron or prism be turned round its axis through half the angle of an equilateral triangle, and so combined with the original figure, it will produce a bipyramidal figure with twenty-four faces, called the Didodecahedron, or a prism with twelve faces instead of six faces. Both of these hex- agonal dodecahedrons are regarded as primary, and they have the same relation to each other as the primary square prisms of the Dimetric system, which resembles the Hexagonal system in being referred to a unique axis. Secondary dodecahedrons are frequently found to occur whose axes are multiples of the axis of the primary dodecahedron, and these secondary dodecahedrons may belong to either system of the primary dodecahedrons. If p denote the parameter of the Hexagonal system, or ratio of the unique axis, to the horizontal or hexagonal axes, we have, First Primary Dodecahedron, . . . i : i : & : p Second Primary Dodecahedron, . . . 2:1:2:^ while the secondary dodecahedrons are represented by the notation, First Secondary Dodecahedron, . . . i : i : : mp Second Secondary Dodecahedron, . . . 2 : i : 2 : mp If the alternate faces of the Hexagonal Dodecahedron be pro- duced, so as to obliterate the intervening faces, a solid is formed of half the origi- nal number of faces, and this solid is called a Rhombohedron. In Figs. 29 and 30 I have shown the hexagonal dodecahe- dron, and its derived rhombohedron, in- scribed in the primary hexagonal prism, so as to show the relation of the solids to each other. The axis AB is the axis of symmetry, and is also called the optic axis. Two different rhombohedrons may be formed out of the same hexagonal do- decahedron, for there are two distinct sets of alternate faces, either of which may be THE RIWMBOHEDRIC SYSTEM. produced, and the two Rhombohedrons so formed have to each other a relation similar to that of the two primary Dodecahe- drons. The primary Dodecahedrons may be confounded by turning either of them through half the angle of an equilateral triangle; and the primary Rhombohe- drons may be confounded by turning either of them through the angle of an equilateral triangle. Many Crystallographers regard the Rhombohedron as the fundamental form of the Hexagonal system, named by them the Rhombohedric system ; and the Hexagonal Dodecahedron is re- garded by them as the result of the combination of the two primary Rhom- bohedrons. The relation between the Fig. 30. Rhombohedron and Hexagonal Dodecahedron is similar to that between the Tetrahedron and Octahedron in the Monometric system, thus 1. The Octahedron maybe converted into one or other of two primary Tetrahedrons by producing its alternate faces ; and the primary Tetrahedrons may be made to coincide by turning either of them through a right angle. 2. The Octahedron may be regarded as a figure produced by the superposition of two Tetrahedrons differing in position by a right angle. In the preceding statements we may substitute the Hexago- nal Dodecahedron for the Octahedron, and the Rhombohedron for the Tetrahedron, provided we at the same time substitute the angle of an equilateral triangle for that of a square. A remarkable form of crystal, frequently occurring in calc ELEMENTS OF NATURAL HISTORY. spar, called Dog- toothed Spar, is shown in Fig. 31, which exhibits its relation both to the primary Rhombohedron and to the primary Hexagonal prism. Theprimary Rhom- bohedron, inscribed in the primary Hexagonal prism, touches the cir- cumscribing prism along the six edges a, b, c, d, e, /, the axis of the prism A'B' coinciding with the axis of the Rhombohedron AB, and being a multiple of it (generally three times its length). If planes be drawn through A' and B', and the edges a, b, c, d, e, f, of the Rhombohe- dron, the twelve-faced figure shown in Fig. 31 will be inscribed in the Hexagonal prism. This remarkable form of crys- tal is commonly called the Scaleno- hedron, and is of frequent occurrence in the Hexagonal or Rhombohedric Fig- 31- system. In the preceding investigation it has been deduced directly from the primary Rhombohedron ; but it may be formed also from the Hexagonal Didodecahedron already described as formed by the combination of the two primary Hexagonal Do- decahedrons. If one half of the faces of the Didodecahedron be produced so as to obliterate the alternate faces, the result will be the Scalenohedron corresponding to the secondary Di- dodecahedron selected for experiment ; and if the axis of this Didodecahedron be three times the axis of the primary Hexagonal Dodecahedron, or Rhombohedron, the Scalenohedron so formed will be the well-known Dog-toothed Calc Spar Crystal. The combinations of forms occurring in the Hexagonal sys- CALC SPAR CRYSTALS. tern are almost endless, some hundreds being described in Calc Spar alone. Two of the most common are exhibited in Figs. 32 and 33. In Fig. 3 2 is shown the combination of the Hexagonal prism with the Rhombo- 3 2 - Fig. 33- hedron, commonly called Nail-head Spar; and in Fig. 33 is shown the combination of the Rhombohedron with the Scaleno- hedron. The following minerals present good examples of crystals oc- curring in the Hexagonal system : 1. Calc Spar. 2. Quartz. 3. Apatite. 4. Beryl. 5. Chabasite, or Gmelenite. 6. Corundum. 7. Tourmaline. CHAPTEE II. CHEMICAL COMPOSITION OF MINERALS. i . Classification of Minerals. A mineral has been already de- fined to be a substance found in the earth, possessing a definite geometrical form, and a definite chemical composition. In the preceding chapter I have explained the general principles of Crystallography, and in the present chapter I shall give the general principles of the classification of minerals, with a short account of those that are of the greatest importance, in conse- quence of their entering largely into the composition of rock masses. The following classification embraces all known minerals in five divisions : 1. Oxygen Compounds. 2. Fluorides and Chlorides. 3. Sulphurets and Arseniurets. 4. Native Elements. 5. Organic Compounds. This classification is based essentially on the Chemical com- position of minerals, and may be readily understood without enter- ing into details, from the following considerations : The exami- nation of the different substances that compose the surface of the earth has led Chemists to admit the existence of sixty-four dis- tinct elements, which cannot be further reduced ; and it may be added, as an interesting fact, that the chemical examination of meteoric stones (which are supposed to reach the earth from the interplanetary spaces) has not led to the discovery of any element in addition to the sixty-four Telluric elements already known. It has been proved by chemists that each of the elements, in ATOMIC WEIGHTS. 2 7 combining with the others, does so in the proportion of certain numbers (or multiples of those numbers), which are called equi- valent mimbers, or Atomic Weights. The following table con- tains the names of the sixty-four elements and their Atomic Weights: Atomic Weights of the Elements. 1. Aluminium, ..... 13^ 2. Antimony, ..... 122 3. Arsenic, ...... 75 4. Barium, ...... 68 5. Bismuth, ..... 210 6. Boron, ...... u 7. Bromine, ...... 80 8. Cadmium, ..... 56 9. Caesium, ...... 123 10. Calcium, ...... 20 1 1 . Carbon, ...... 6 12. Cerium, ...... 47 13. Chlorine, ..... 35^ 14. Chromium, ..... 26^ 15. Cobalt, ...... 29^ 16. Copper, ...... 31! 17. Didymium, ..... 48 1 8. Erbium, ...... x 19. Fluorine, ..... 19 20. Glucinum, ..... 7 21. Gold, ....... 196^ 22. Hydrogen, 23. Iodine, .... 24. Iridium, ...... 98^ 25. Iron, ..... v . 28 26. Lanthanum, .... 47 27. Lead, ....... 1031 28. Lithium, ...... 7 29. Magnesium, ..... 12 30. Manganese, ..... 27 \ 31. Mercury, ..... 100 32. Molybdenum, .... 48 i 127 33. Nickel, 29^ 34. Niobium, x 35. Nitrogen, 14 36. Norium, .... . x 37. Osmium, 99^ 38. Oxygen, 8 39. Palladium, 53^ 40. Phosphorus, 31 41. Platinum, 98^ 42. Potassium, 39 43. Ehodium, 52 44. Rubidium, 85 45. Ruthenium, 52 46. Selenium, 39! 47. Silicon, 21 48. Silver, 108 49. Sodium, 23 50. Strontium, 43^ 51. Sulphur, 16 52. Tantalum, . . . . 6?| 53. Tellurium, 64^ 54. Terbium, x 55. Thallium, 204 56. Thorinum, 39^ 57- Tin, 59 58. Titanium, 25 59. Tungsten, ..'... 92 60. Vanadium, 68 6 1. Uranium, 60 62. Yttrium, x 63. Zinc, 32^ 64. Zirconium, 334 28 ELEMENTS OF NATURAL HISTORY. Many of these elements are so rare as to be merely objects of scientific curiosity with chemists, and many others enter into the composition of minerals, that seldom form constituents of rock masses ; so that, of the whole number of elements and minerals known, it is not necessary to have a minute knowledge of more than one-fourth. By far the most important of all the elements, are oxygen and sulphur, which, owing to their powerful affinities, enter into more mineral combinations than any other elements ; after these come carbon and silicon, and then follow fluorine, chlorine, phos- phorus, arsenic, and aluminium. Arranging the elements in the order of practical importance, and placing after each the names of the groups of minerals de- rived from it, we have 1 . Oxygen, producing the Oxidized Stones. 2. Sulphur, the Sulphurets and Sulphates. 3. Carhon, the Carbonates. 4. Silicon, the Silicates. 5. Fluorine and Chlorine, ,, the Fluorides and Chlorides. 6. Phosphorus, ,, the Phosphates. 7. Arsenic, the Arseniurets and Arseniates. 8. Aluminium, Compounds of Alumina. The first subdivision of minerals contains the Oxygen Com- pounds, which may be again subdivided as follows : Oxygen Compounds. 1. Simple Oxides. 2. Compound Oxides. 3. Silicates. 4. Tantalates, Titanates, Vanadates. 5. Sulphates. 6. Borates. 7. Phosphates. 8. Nitrates. 9. Carbonates. CLASSIFICATION OF MINERALS. 29 2. The Simple Oxides. Under the name of Oxides are in- cluded both the Simple and Compound Oxides of elementary bodies ; and there are several elements that furnish such com- pounds, viz., silicon, aluminium, iron, copper, titanium, &c. The following are the Simple Oxides most frequently met with in nature : A. Quartz Family. This is the most abundant of all mine- rals, and enters freely into combination with many of the elements. It is composed of one atom of silicon, combined with three atoms of oxygen, and therefore contains Silicon, .... 2 1 .... 46^ per cent. Oxygen, .... 24 .... 53^ 45 1O Pure Quartz occurs in crystals of the Hexagonal system (Figs. 27 and 28), and is either colourless and limpid, or va- riously coloured and more or less opaque, giving rise to the varieties called smoked quartz, rose quartz, &c. Quartz, or pure Silica, is nearly insoluble in water and com- mon acids, but under favourable circumstances may be taken up by water in quantities sufficiently large to become appreciable after a long lapse of time. Thus, the water of the Geysers in Iceland contain TSJOO P er cent - ^ Silica, and sea water contains sometimes Yoo 3 oo o~ P er cen ^ Quartz forms an important constituent of many rocks, such as Quartzite, Sandstone, Granite, &c., and the following are the principal varieties of this mineral : (a.) Amethyst. A violet-coloured quartz. (i.) Chalcedony. An opaque variety, containing a small quantity of water in combination with the Silica, and coloured of various shades, from white to red ; contains the stones called Carnelian. (c.) Agate. Consists of alternate layers ofpureQuartz and Chalce- dony, variously coloured, and called, from the forms of the 3 ELEMENTS OF NATURAL HISTORY. layers exposed in section, fortification agate, ring agate, &c. It occurs chiefly, deposited from solution in water, in cavities (geodes) of volcanic rocks and in mineral veins. (d.} Jasper Opaque quartz, coloured yellow, red, &c., by peroxide of iron intimately associated with it. It is found in the bog iron ore of Germany, in pebbles rolled by water in the sand of the Nile and Desert of Egypt, and in small subordinate beds elsewhere. (e.~) Elint. Semi-opaque quartz, deposited in limestone rocks in the form of nodules, probably by the help of organic agency ; the dark-coloured flints are found in white chalk and white Jura limestone, and owe their colour to carbon ; the light- coloured flints are called chert, and are frequently found to contain fossil corals, wood, &c. ; and the pure black flints are called Lydian stone, still used as a touchstone for testing the purity of gold. (/. ) Opal. Opal is quartz, containing from 4 to i o per cent, of water in combination. The precious or fire opal exhibits a play of colours of bright hyacinth red and yellow, and is found in cavities of the trachyte rocks of Hungary ; the limpid colourless variety, called Hyalite, is found in Mexico and in the Mourne Mountains in basalt and granite ; and the brown opaque variety, called Menilite, forms knobs and layers in the adhesive slate of Menil Montant, near Paris. B. Corundum This mineral is of rare occurrence, but is very interesting, both on account of its composition and the extreme beauty of some of its varieties. It is, like quartz, a simple oxide, consisting of two atoms of aluminium and three atoms of oxygen. Hence its composition is Aluminium, .... 27.5 .... 53.4 per cent. Oxygen, 24.0 .... 46.6 ,, MINERAL OXIDES. 31 Corundum is sold as Emery, and occurs massive, in metamor- phic rocks, in Xaxos and Saxony ; the precious varieties are transparent, and are found in alluvial beds in Ceylon, China, and Siam. When blue, it is called Sapphire, and when red, it is called Ruby. The transparent green variety is comparatively little known, and is found in Siam. Corundum crystallizes in the Hexagonal system, and exhibits a great variety of secondary dodecahedrons. C. Oxides of Iron. There are two important oxides of iron, used frequently as ores, and named the Red and Brown Haema- tite. (a.) Red H&matite. Occurs in crystals, as specular iron ore and micaceous iron ore in the Rhombohedric or Hexagonal sys- tem ; when massive, it is of a deep red colour, its pow- der being named rouge. It is an oxide of iron, similar to the oxide of aluminium known as Corundum, and has the following composition : Two atoms of Iron, .... 56 .... 70 per cent. Three atoms of Oxygen, ... 24 .... 30 ,, 80 100 (b.} Brown Hcematite is a hydrated variety of the former, and con- tains somewhat variable proportions of water, ranging from 10 to 20 per cent. It bears the same relation to Red Haema- tite that Opal does to Quartz. Like most minerals formed by deposition from water, it occurs frequently in the form of incrustations and stalactites, attached to other rocks. D. Oxides of Manganese. There are many oxides of Manga- nese, used as ores of this metal for the production of chloiine gas for manufacturing purposes. The most important and valu- 32 ELEMENTS OF NATURAL HISTORY. able of these ores is the mineral called Pyrolusite, which has the following composition : One atom of Manganese, . . 27.5 . . . 63.2 per cent. Two atoms of Oxygen, . . . 16.0 . . . 36.8 43-5 The other oxides of Manganese are named Hausmannite, Braunite, Manganite, and Psilomelane ; they are all of less value, and most of them of much rarer occurrence, than Pyrolusite. E. Oxides of Copper. There are two oxides of Copper, known to miners as Red and Black Copper ore. (a.) Red Copper Ore. Occurs in Octahedrons and Ehombic Dode- cahedrons of the Figs. 5 and n, Afonometric system, and has the composition Two atoms of Copper, . . . 63.5 . . . 88.8 per cent. One atom of Oxygen, ... 8.0 ... 11.2 71.5 100.0 (5.) Black Copper Ore. This mineral is generally found massive, but has been occasionally met with, crystallized, in cubes. It contains only one atom of Copper. One atom of Copper, . . . . 31.75 . . 79.8 per cent One atom of Oxygen, .... 8.00 . . 20.2 39.75 100.0 The oxides of Copper are usually met with in the shallow parts of metallic lodes, and are produced by the oxidation of the Sulphurets of Copper, caused by the contact of water and atmo- spheric air with the sulphurets in the upper parts of the lodes. F. Tinstone. This remarkable and valuable ore is the only OXIDES OF COPPER AND TIN. 3 3 known source of metallic Tin. It is an oxide of the metal, hav- ing the following composition : One atom of Tin, .... 59 .... 7 8| per cent Two atoms of Oxygen, .. 16 .... ail n 75 100.0 Tinstone occurs in crystals of the Dimetric system (Fig. 18), and has been found in Cornwall from the most remote antiquity . it is also found in small quantities in Saxony, Austria, and Fin- land ; and in very large quantities in the Malaccas, and in Banca, in the East Indian Isles. Herodotus, 450 B. c., alludes to Corn- wall, under the name Cassiterides, and it is believed that the Phoenicians traded in Tin between Tyre and Tarshish, in Spain, from the earliest ages. There is, also, good reason for supposing that the tinstones of Cornwall, having been landed in Gaul, were afterwards carried on horseback across that country, by a thirty days' journey, for shipment to the East, on the shores of the Mediterranean. The present annual production of Tin is as follows : Cornwall, _ 140,000 cwt. Banca and Malacca, 100,000 ,. Saxony, 3,500 Austria, 380 Sweden and Finland, 750 Total, .... 244,630 cwt. G. Oxide of Titanium. Titanium occurs in nature combined with oxygen in the following proportions : One atom of Titanium, ... 25 .... 6 1 per cent Two atoms of Oxygen, ... 16 .... 39 41 100.0 34 ELEMENTS OF NATURAL HISTORY. Titanic acid, or oxide of Titanium, is found as three distinct minerals, which have all the same composition (a.) Rutile Dimetric, prismatic forms. (b,~) Anatase Dimetric, octahedric forms, (c.) Brookite Trimetric. It forms a remarkable example of a mineral occurring in two distinct crystalline systems, and yet having the same chemical composition. This phenomenon is called Dimorphism, and is illustrated also by the cases of Sulphur and Cole Spar. Sulphur occurs in the Trimetric and Monoclinic systems. Calc Spar occurs in the Rhombohedric and Trimetric systems. 3. The Compound Oxides. Under the name of Compound Oxides are included all the minerals formed by the combination of one or more oxides, which are not of sufficient importance to form classes by themselves. Other groups of minerals, such as Silicates, Sulphates, Borates, Phosphates, Nitrates, and Carbo- nates, are as truly compound oxides as those included in the pre- sent group ; but they are so important as to require separate mention in our classification ; and in this instance, as in many others in mineralogy, scientific precision is sacrificed to conve- nience of description. A. Spindle. This mineral, when pure, has the following composition : One atom of Alumina, ... 51.5 ... 7 2 per cent. One atom of Magnesia, . . . 20.0 ... 28 ,, 7 1 .o i oo The pure Spinelle of Ceylon is reddish pink, and occurs in the Monometric system in octahedrons ; its magnesia is often more or less replaced by the oxides of iron, zinc, and manganese, which alter the colour of the mineral from pink to brown and black, without changing its form, which is always the octahedron of Euclid (Fig. 5). This change of composition, within certain THE COMPOUND OXIDES. 35 limits, while the crystallographical form remains the same, is called Isomorphism, and is the converse of the phenomenon al- ready described as Dimorphism, which implies change of crys- talline form with identity of composition. B. Magnetic Iron Ore. This mineral occurs in octahedrons of the Monometric system, and forms, when massive, the cele- brated "lodestone" of the ancients. Its composition is as fol- lows : One atom of Peroxide of Iron, . 80 ... 68.4 per cent. One atom of Protoxide of Iron, . 36 ... 31.6 116 100.0 It is one of the most valuable of the ores of iron, and is found in large quantities in the metamorphic rocks of Sweden and Nor- way. It is closely allied to the compound oxides called Chrome Iron Ore, and Titaniferous Iron Ore, which are of frequent occur- rence in similar deposits. 4. The Silicates. As Silica is the most abundant of all the oxides, so we find the Silicates to be the most important of all the compound oxides, and to enter more largely than any other minerals into the composition of rock masses. The Silicates may be divided, for convenience of description, into the following families : Silicates. 1. Felspar Family. 2. Hornblende Family. 3. Mica Family. 4. Talc Family. 5. Zeolite Family. 6. Andalusite Family. 7. Garnet Family. 5 . The Felspar Family. The Felspars form the chief consti- tuent of almost all the rocks produced by igneous agency, or me- D2 36 ELEMENTS OF NATURAL HISTORY. tamorphic rocks produced by the joint action of water and heat. Some of the felspars belong exclusively to the oldest granites, and others are equally characteristic of the most modern volcanic rocks, so that they admit of a geological, as well as of a chemical or mineralogical classification. A. Orthoclase or Potash Felspar. This mineral occurs in crystals of the Monoclinic system, often combined in twins or macles. It is found chiefly in the granite rocks, of which it is a characteristic constituent. Orthoclase, when perfectly pure, con- sists ofa double or compound silicate of alumina and potash, and has the following composition : Four atoms of Silica, . . 180.0 . ... 64.8 per cent. One atom of Alumina, . 51.5 .... 18.4 ,, One atom of Potash, . . 47.0 .... 16.8 278.5 100.0 The foregoing may be regarded as the typical constitution of Orthoclase, but it is found in practice that it is never perfectly pure, as some of the potash is always replaced by soda, lime, and magnesia, in small quantities, without any alteration in the crystalline form of the mineral. The following is the mean of seven analyses of different specimens collected from the granite of Leinster, which is seventy miles in length, and forms the largest mass of granite in the British Islands. Orthoclase Felspar (Leinster). Silica, 64.59 .... 65.05 per cent. Alumina, 18.31 . . . . 18.44 Potash, 12.23 12-32 ., Soda 2.75 .... 2.77 Magnesia, 0.58 .... 0.58 ,, Lime, 0.25 .... 0.2*5 Water, 0.58 .... 0.59 ,, 99.26 100.0 SILICATES. 37 The silica and alumina, in this analysis, are the same as in the typical Orthoclase, but the potash is partially replaced by soda, &c. The following are the principal varieties of this important mineral : (a ) Adularia or Moonstone. A colourless, semi transparent va- riety. (b.) Sanidine, or Glassy Felspar. A vitreous, creviced, transparent Orthoclase, never found in granitic rocks, but characteristic of the volcanic rocks called Trachyte. (c.) Sunstone. This is a name given to semitransparent felspars (sometimes oligoclase), which in crystallising have entangled minute scales of oxide of iron, which are scattered through the mineral, and give a reflection of light, much admired by jewellers. (rf.) Amazon Stone. This is a green felspar, found in Siberia and Greenland ; that of Siberia owes its green colour to copper, and that of Greenland, to iron protoxide. B. Albite, or Soda Felspar This felspar has the same com- position as Orthoclase, with the exception that soda is substituted for potash. When perfectly pure, its composition is< Four atoms of Silica, . . 180.0 .... 68.7 per cent One atom of Alumina, . 51.5 .... 19.5 One atom of Soda, . . . 31.0 . . . . n.8 262.5 Albite is a much rarer mineral than Orthoclase, but is found associated with it as a constituent of the granites of the Mourne Mountains ; its soda is partly replaced by potash, lime, and mag- nesia, without changing its crystallographic form, which is tri- clinic and essentially distinct from that of Orthoclase, which is monoclinic ; this is one of the arguments used by mineralogists to 3 8 ELEMENTS OF NATURAL HISTORY. prove that potash and soda are not isomorphous in their combina- tions. The following is the composition of the Albite found in the granite of the Mourne Mountains : Albite Felspar (Mourne). Silica, . . . . 68 97 per cent. Alumina, . . . 19.23 ,, Soda, 8.71 Potash, .... 1.56 Lime, .... 1.21 ,, Magnesia, ... 0.24 Loss, 0.08 It is evident, on comparing the foregoing analysis with the theoretical composition of Albite, regarded as a double silicate of alumina and soda, that its silica and alumina are the same as those of the perfect mineral, while its soda is partly replaced by potash, lime, and magnesia. C. Oligoclase, or Soda and Lime Felspar. This felspar, like the two preceding, is often found as a constituent of granite, and occurs in this connexion in Donegal, Scotland, and Sweden. It is triclinic in the form of its crystals ; and contains less silica than either orthoclase or albite, for it has only three atoms of silica to one of alumina, and one of soda and lime mixed ; when quite pure, its composition is Three atoms of Silica, . . 135.0 ... 62.50 per cent. One atom of Alumina, . . 51.5 . . . 23.84 Half atom of Soda, . . . 15.5 . . . 7.18 Half atom of Lime, , . . 14.0 . . . 6.48 216.0 The following analysis shows the actual composition of the Oligoclase of Donegal : FELSPARS. 39 Oligoclase Felspar (Donegal}. Silica, 59-92 . 60.56 per cent. Alumina and Per- ) oxide oflron, } ' ^ ' ' * 25 ' 12 Soda, 6.47 ... 6.54 Lime, 5.30 . . . 5.35 Potash, 2.07 . . . 2.09 Magnesia, 0.13 ... 0.13 Protoxides of Iron ) } . . . 0.21 . . . 0.21 and Manganese, J 98.95 100.00 Oligoclase is an essential ingredient, associated with Horn- blende, in many syenites, and other trap rocks. D. Lalradorite. This is a lime, or lime and soda felspar, consisting essentially of a double silicate of alumina and lime, having the following composition : Two atoms of Silica, . . 90.0 .... 53.1 per cent. One atom of Alumina, .. 5 1.5 .... 30.4 One atom of Lime, . . . 28.0 .... 16.5 169.5 100.0 Labradorite is triclinic in its crystallization, and is often found to afford a rich play of iridiscent colours, but is sometimes quite white. It is found occasionally in metamorphic beds of gneiss, but does not occur in granite. The following analysis shows the actual composition of the Labradorite found in Loch Scavig, in Skye, as a constituent of the celebrated Syenite of that locality: Lalradorite Felspar Silica, .... 53.60 . . . 53.44 per cent. Alumina, . . . 29.88 . . . 29.80 Lime, .... 11.02 . . . 10.99 Soda, .... 4.92 . . . 4.90 Potash, .... 0.80 . . . 0.80 Magnesia, . . . 0.07 . . . 0.07 ,, 100.29 100.0 40 ELEMENTS OF NATURAL HISTORY. This analysis shows that some of the lime of the theoretical mi- neral is replaced in nature by soda, without any alteration of form or other physical qualities. It would almost appear, from a comparison of many Labradorites, especially those found in the metamorphic rocks of Eggersund, in Norway, as if the soda re- placed the lime in composition, in the proportion of one atom to three. This supposition gives us a theoretical formula for Labra- dorite, viz. : Two atoms of Silica, .... 90.00 . . . 52.9 per cent. One atom of Alumina, .... 51.50 . . . 30.2 Three-fourths of an atom of Lime, 21.00 . . . 12.3 ,, One-fourth of an atom of Soda, . 7.75 . . . 4.6 170.25 The agreement of this theoretical formula with the actual analysis of Labradorite is very close. E. Anorihite. This is a lime felspar, and is found in many trap rocks, but is unknown in granites. It is a double silicate of lime and alumina, having the following theoretical composition: Three atoms of Silica, ... 135 ... 45.9 per cent. Two atoms of Alumina, . . 103 . . . 35.0 Two atoms of Lime, .... 56 ... 19.1 294 i oo.o Anorthite is the most basic of all the felspars, and has been frequently found in lavas and meteoric stones. A remarkable trap rock occurs in Carlingford mountain, composed of Anorthite and Augite ; the Anorthite has the following composition : Anorihite Felspar (Carlingford}. Silica, 45-87 Alumina, 34-73 Lime, 17.10 Magnesia, ..... 1.55 99-^5 FELSPARS. 4 1 Here we see that the lime is partially replaced by magnesia. Collecting together into one table the compositions of the five felspars, we obtain as follows arranging them according to their richness in Silica : Albite. Orthoclase. Oligoclase. Labrudorite. Anorthite. Silica, .... per cent. 68.7 per cent. 64.8 per cent. 62.5 per cent. 5 2 -9 per cent. 45-9 Alumina, . . . 19-5 18.4 23-8 30.2 35-o Potash, .... 16.8 Soda, ... n. 8 7- 2 4.6 Lime, .... 6-5 12.3 19.1 F. Leucite. This remarkable mineral performs the function of a true felspar in volcanic rocks, and has never been found in any rocks, except the lavas and traps. It occurs in crystals hav- ing the form of the Deltoidal Octahedron (Fig. 16), which is often called, after this mineral, the Leucitohedron. Its colour is greyish white, its lustre glassy, and it is semitransparent. It has the following composition: Eight atoms of Silica, . . . 360.0 . . . 54.9 per cent. Three atoms of Alumina, . . 154.5 2 3-6 ,, Three atoms of Potash, . . 141.0 . . . 21.5 ,, 655.5 100.0 Leucite abounds in trachyte between Lake Laach and Andernach, on the Rhine, but the finest crystals are found in the lavas of Vesuvius, and in the old lavas near Rome. It is remarkable, historically, as the mineral in which Klaproth first discovered that potash (so called vegetable alkali) was a consti- tuent of the mineral kingdom. The analysis of Klaproth is so interesting and accurate, that I add it here, for the purpose of comparison with the theoretically perfect type given above. 4 ELEMENTS OF NATURAL HISTORY. Leucite Felspar ( Vesuvius}. Silica, 53.75 Alumina, 24.63 Potash, 21-35 99-73 G. Nepheline, or ElcBolite. This mineral, like Leucite, may be regarded as a volcanic, or semivolcanic felspar. It occurs in the hexagonal system of crystals, with a hasic cleavage showing hexagons imbedded in the rock in which it occurs. The variety known as Nepheline is colourless, and is found in volcanic rocks only, in which it performs the functions of a true felspar. The variety known as Elc&olite has various shades of colour green, brown, red, and is massive, with a glassy lustre on its surfaces of cleavage, and an eminently resinous lustre on its surfaces of cross fracture, from which it derives its name. El&olite forms a connecting link between the volcanic rocks and the older plutonic rocks, by entering largely into the composition of Zircon Syenite, in Norway and in the Ural Mountains. It has the following composition : Three atoms of Silica, . . 135 . . . . 45.0 per cent Two atoms of Alumina, . . 103 .... 34.3 Two atoms of Soda, ... 62 .... 20.7 300 100.0 I add here, for the purpose of comparison, Arfvedson's ana- lysis of pure Nepheline from Monte Somma. Nepheline Felspar (Monte Somma). Silica, . . . . 44.11 Alumina, . . . 33.73 Soda, .... 20.46 Water, .... 0.62 98.92 VOLCANIC FELSPARS. 43 The soda in Nepheline is often partially replaced by potash, just as in Leucite, the potash is sometimes partly replaced by soda. Leucite and Nephe.line are, in fact, the potash and soda felspars of the volcanic rocks, just as Orthoclase and Albite are the potash and soda felspars of the plutonic rocks ; and this ana- logy is carried out even in the forms of the crystals, for Nepheline and Leucite are Hexagonal and Monometric respectively, while Albite and Orthoclase are, respectively, triclinic and monoclinic ; in each case the most complex form of crystal belonging to the mineral in which soda largely occurs. 6. The Hornblende Family. This important group of mine- rals is chiefly interesting in consequence of its entering exten- sively into the composition of rocks of igneous origin ; most of these rocks are formed principally of a felspar and of a hornblende, which seem to be the opposite, poles round which the different elements grouped themselves on cooling. The Felspar family is remarkable for containing large quantities of alkalies and lime, while the Hornblende family, on the other hand, appropriates to itself quantities of iron and magnesia. A. Hornblende. This well-known mineral occurs in crystals of the Monoclinic system, having cleavage planes that form angles of 124^ and 55J ; being nearly those of a regular hexagon and equilateral triangle. It is generally of various shades of green, up to black, according to the quantity of iron it contains. Hornblende may be regarded as a compound of three atoms of silica with four atoms of magnesia, lime, or protoxide of iron, and its composition varies with the preponderance of one or other of these bases. The following are the chief varieties of hornblende : (.) Tremolite. This is a magnesia and lime hornblende, quite white, and not found in the igneous rocks; it is usually found in metamorphic limestone, especially in the metamor- 44 ELEMENTS OF NATURAL HISTORY. phic dolomite of the Val Tremola, St. Gothard, from which locality it derives its name ; semi-transparent. (b.) Actinolite. This is a hornblende, of a beautiful grass green, due to the presence of 6-8 per cent, of protoxide of iron ; it is found generally in metamorphic talcose slates, and never in igneous rocks ; semi-transparent. (c.) Hornblende proper. Colour dark green or black, opaque ; contains large quantities of iron and of alumina, which ap- pears partially to discharge the duty of silica. It is one of the most important of rock minerals, and constantly ap- pears as a constituent of the igneous rocks. B. Augite. This mineral is closely allied to hornblende, but differs from it in crystalline form, and slightly in chemical com- position. It occurs in the Monoclinic system, with cleavage planes making nearly a right angle with each other. Its compo- sition consists of two atoms of silica combined with three atoms of magnesia, lime, or iron protoxide; and, like hornblende, it varies greatly with the change of base. The chief varieties of augite are (a.) Diopside, or white Augite. This variety corresponds with Tremolite, and contains no iron; found in metamorphic rocks. (b.) Sahlite. Contains some iron, which gives it a pale green colour ; corresponds to actinolite. (0.) Augite proper, or Pyroxene. Green to black in colour; forms an essential constituent of the more modern igneous rocks, free from quartz ; like Hornblende proper, this mineral con- tains alumina that seems to replace some of the silica, and discharge its functions. The difference between hornblende and augite is only slight, and appears, in the case of the igneous rocks, to have been oc- casioned by slight differences in physical conditions in the cooling HORNBLENDES. 45 of the rock, and slight chemical differences in the composition of the rock paste, such as the presence or absence of free silica. Hornblende, as a rule, characterizes the older igneous rocks, and Augite, the more modern. I add here, for the sake of comparison, the analyses of two Augites, one from Carlingford, associated with Anorthite felspar ; and the other from Loch Scavig, Skye, associated with Labrado- rite felspar. Augite (Carlingford and Scavig}. Carlingford. Scavig. Silica, 50.72 .... 50.80 Alumina, 9.36 .... 3.00 Protoxide of Iron, . . 18.61 .... 9.61 Lime, 16.96 .... 19.35 Magnesia, 2.40 .... 15.06 Soda, .... 0.44 Potash, .... 0.22 Protoxide of Manganese, .... 1.08 98.05 99.56 The Augite of the Anorthite Syenite abounds in iron ; that of the Labradorite Syenite, in magnesia. 7. The Mica Family This group of minerals is easily re- cognized by their remarkable foliation, which occurs to a degree not known in any other family of minerals. They are found in the igneous rocks, and in metamorphic rocks, and are eminently characteristic of the rock masses in which they are found. They are divisible into two groups, the first of which is characterized by the large amount of alumina and potash (or other alkalies) found in it, and the second by the large quantity of iron and magnesia that form essential constituents of the mineral. These two groups are also distinguishable by their optical pro- perties, being binaxial and uniaxial respectively and are also, in general, distinguishable by their colours, as the second group has a dark colour, due to the presence of iron. 46 ELEMENTS OF NATURAL HISTORY. A. White, or Binaxial Mica. This mineral is found in crys- tals of the Trimetric system, with an eminently basal cleavage, and with angles in its primary rhomb not differing much from 120, or the angle of the regular hexagon. White Mica consists essentially of one atom of silicate of potash, combined with m atoms of silicate of alumina m is generally 4, 3, or 2. (a.) Muscovite. This is the name given to white mica, when m = 4, or m = 3 ; its composition in these two cases is m - 4. Five atoms of Silica, . .. 225 .... 47.1 per cent. Four atoms of Alumina, . 206 . . . 43.1 One atom of Potash, ... 47 .... 9.8 478 100.0 = 3. Four atoms of Silica, . . 180.0 .... 47.2 per cent. Three atoms of Alumina, . 154.5 4-5 One atom of Potash, . . 47.0 .... 12.3 381.5 100.0 This form of white mica has not been yet found among Bri- tish granites, but is said to occur elsewhere. (I.} Margarodite. This is the white mica in which there is one atom of water, and m - 2. Three atoms of Silica, .. 135 .... 45.9 per cent. Two atoms of Alumina, . . 103 .... 35.0 One atom of Potash, ... 47 .... 16.0 One atom of Water, ... 9 .... 3. i 294 100.0 Margarodite is the white mica of the Irish granites, and occurs abundantly in Leinster and Donegal. Its average compo- sition in these two districts is as follows : MICAS. 47 Margarodite Mica (Donegal] . Silica, 45.02 .... 45.02 Alumina, , . -i c.6.4. \ T T> M \ 37- 88 Iron Peroxide, 2.24) Potash, 11.44^ Soda, 0.43 Lime, 0.48 *> . . . 13.77 Magnesia, 0.71 Iron Protoxide, 0.71 ! Water, 3.00 .... 3.00 99.67 Margarodite Mica (Zeinster). Silica, ........ 44.58 .... 44.58 Alumina, 32.13 ) ... 36.62 Iron Peroxide, 4.49 ) Potash, 10.67 I Soda, 0.95 Lime, 0.78 > . . 3- 2 3 Magnesia, 0.76 Iron Protoxide, 0.07 Water, 5.34 .... 5.34 99-77 In these analyses we see, as frequently happens in other cases, that part of the alumina is replaced by iron peroxide, and part of the potash hy soda and the earths. (c.) Lepidolite. This is a binaxial mica, of a pink or reddish colour, in which potash is largely replaced by the rare alkali, lithia. It is found only in beds of granite and gneiss, near tin or other metallic lodes, and does not form a con- stituent of rock masses, on a large scale. B. Black, or Uniaxial Mica. The white micas just described are remarkable for containing large quantities of alumina and potash, or other alkalies, but contain very little iron or mag- 4 8 ELEMENTS OF NATURAL HISTORY. nesia ; the black or uniaxial micas, now to be noticed, contain, on the contrary, large quantities, either of magnesia, or of iron, or of both. They possess the characteristic appearance of mica, and are generally of a dark colour brown, green, or jet black; they are found in crystals, quite flat and sectile, generally hexagons, and are considered to belong to the hexagonal system. There are two kinds of Uniaxial Mica, Biotite and Lepidomelane ; in the first of which there is a large quantity of magnesia, and in the second, a large quantity of iron. (a.) Biotite) or Magnesian Mica. Colour dark green, brown, or black ; crystalline system hexagonal. Has usually the fol- lowing composition : Biotite Mica (Lake Baikal]. Silica, 42.01 Alumina, 16.05 Iron Peroxide, 4.93 Magnesia, 2 5-97 Potash, 7.55 Water? 2.28 98.79 (b.) Lepidomelane, or Iron Mica. Colour jet black, due to the presence of manganese ; from this circumstance, this mica is called by Breithaupt, the Haven Mica ; occurs in the hexa- gonal system of crystals. It was formerly considered a rare mineral, but is now well known to be the common kind of black mica, that usually occurs in granite rocks. It is found in the granites of Leinster, Donegal, and Sweden, with the following compositions : Lepidomelane Mica (Leinster, Donegal, Sweden}. Leinster. Donegal. Sweden. Silica, 35.55 . . . 36.20 . . . 32.60 Alumina, 17.08 . . . 15.95 . . . 15.56 Iron Peroxide, .... 23.70 . . . 27.19 . . . 27.94 THE TA L C FA MIL Y. 49 Leimter. Donegal. Sweden. Potash, 9-45 8.65 . . . 4.30 Soda, 0.35 . . . 0.16 . . . 0.82 Magnesia, 3.07 . . . 5.00 . . . 4.79 Lime, 0.61 . . . 0.50 . . . 1.15 Protoxide of Iron, .... 3.55 . . . 0.64 . . . 7.45 Protoxide of Manganese, . 1.95 ... 1.50 . . . 0.80 Water, 4.30 . . . 3.90 . . . 6.80 99.61 99-^9 8. The Talc Family. This constitutes a very important group of minerals, which agree in containing large quantities of magnesia or iron, and in showing a strong tendency to assume hydrated forms, in consequence of the metamorphic action of water, doubtless aided by a high temperature. The family con- tains three principal members ; viz. : A. The Talcs. B. The Serpentines. C. The Chlorites. A. The Talcs Talc is a mineral rarely crystallized, occurring in foliated or scaly masses ; it resembles mica in its cleavage, and has always a greasy* feel ; its laminae are flexible, but not elastic, like those of mica ; and it has a mother of pearl lustre. "When pure, it has the following composition : Five atoms of Silica, . . 225 .... 63.6 per cent. Six atoms of Magnesia, . . 120 . . . . 33.9 One atom of Water, ... 9 .... 2.5 354 ioo. o (.) Talc forms an important constituent of the metamorphic granites and gneiss rocks of the Alps, and is found to * The peculiar feel of a mineral, which is called greasy, seems to me to be confined to the highly magnesian silicates, and to the hydrated aluminous silicates. E 50 ELEMENTS OF NATURAL HISTORY. enter into the composition of many of the beds that flank the main chain of those mountains, although it is excluded from the granites proper, that form the true axis of the chain. The granitoid metamorphic gneiss, in which talc is found, is called Protogene. The following analysis of talc from the protogene rocks of Handeck, near the Grimsel, is added for the purpose of comparison with the typical talc. Talc (GrimseT). Silica, 61.20 Alumina, 0.60 Peroxide of Iron, 2.38 Magnesia, 30.80 Lime, 0.23 Potash, o.i i Soda, 0.06 Iron Protoxide, 0.92 "Water, 1.20 97-5 (b.} Meerschaum is a form of hydrated talc, having a definite composition. (c.) Steatite, or German Soapstone, is also an hydrated talc. ( 2 9a> an( i 2 8- When the cobalt preponderates, the mineral is called Smaltine; and when nickel predominates, it is called Cloanthite ; when both disappear, or nearly so, an arseniuret of 90 ELEMENTS OF NATURAL HISTORY. iron is left, which is called Leucopyrite, and occurs in a different crystalline system, having become trimetric. Leucopyrite has the composition One atom of Arsenic, .... 75 ... 72. 8 per cent. One atom of Iron, 28 ... 27.2 ,, 103 100.0 Leucopyrite has a silver white colour, merging into steel grey, with a metallic lustre ; it is found as an accidental mineral in many rocks, especially serpentine, and in metalliferous lodes. Q. Mispickel. This mineral is an arsenio-sulphuret of iron, having the same chemical composition as Nickel, or Cobalt Glance ; viz. : Two atoms of Sulphur, ... 32 ... 19. 6 per cent. One atom of Arsenic, .... 75 ... 46.0 Two atoms of Iron, .... 56 ... 34.4 ,, 163 100.0 Mispickel, therefore, bears the same relation to the glance ores of cobalt and nickel, that Leucopyrite bears to Smaltine and Clo- anthite. It is trimetric like Leucopyrite, instead of monometric, as the corresponding ores of cobalt and nickel are ; and this fact serves to show that iron, although capable of replacing nickel or cobalt, atom for atom, is not isomorphous with those metals. Mispiclcel is generally found in short prismatic or tabular crystals, singly imbedded, or attached in groups ; also massive, in granu- lar or fibrous aggregates ; colour silver white, inclining to steel grey; lustre metallic. Mispickel is frequently met with in veins of ore, and is also an accessory ingredient in many crystalline schists and also in serpentines. R. Copper Pyrites. This well-known and most valuable ore of Copper is a double sulphuret of copper and iron, having the following composition : 7 HE SULPHURETS. 9 1 Four atoms of Sulphur, . . 64.0 . . . 34.9 per cent. Two atoms of Copper, . . . 63.5 . . . 34.6 Two atoms of Iron, .... 36.0 . . . 30.5 Copper Pyrites is monometric, and affects chiefly the Octa- hedric and Tetrahedric forms of that system ; it has a metallic lustre, and is of a brass yellow colour, liable to tarnish readily, and often iridescent. Copper Pyrites, or Yellow Copper Ore forms the principal ore of Copper found in Cornwall, where upwards of 150,000 tons of this ore are raised annually ; it is associated in several mines of that county with Tinstone, Erubescite, Copper Glance, Galena, Grey Copper Ore, and Blende. No metallic mineral is liable to more changes, from the metamorphic action of air and water, than Copper Pyrites. The following are several of the products of this metamorphic action, which takes place incessantly in lodes : (.) Slue Vitriol. Hydrated sulphate of Copper. (b.) Malachite. Hydrated carbonate of Copper, (c.) Chrysocolla. Hydrated silicate of Copper. (d.) Black Copper Ore Oxide of Copper. (e.) Limonite Hydrated oxide of Iron. S. Grey Copper Ore. This complex and variable ore is easily recognized by its tetrahedric form, whenever it occurs in crys- tals ; so much so, indeed, as to occasion the name Tetrahedrite, often given to it by mineralogists ; it has a metallic lustre ; colour between steel grey and iron black ; rather brittle, with uneven subconchoidal fracture. There is no ore of copper or silver known that is more com- plex or variable in composition than Grey Copper Ore. It con- sists essentially of four atoms of a basic sulphuret, combined with one atom of an acid sulphuret. 92 ELEMENTS OF NATURAL HISTORY. The basic sulphurets may be any combinations or proportions of the following : 1. Copper Glance. 2. Erubescite. 3. Silver Glance. 4. Magnetic Pyrites. 5. Blende. 6. Cinnabar. 7. Galena. while the acid sulphurets are always r. Stibnite. 2. Orpiment. This remarkable ore, therefore, may contain sulphur, arsenic, antimony, mercury, zinc, iron, silver, and lead. The most im- portant varieties of this mineral are those in which copper, silver, or mercury, preponderate ; they are called, respectively 1. Grey Copper Ore (Kupfer fahlerz), .... 37 per cent. Copper. 2. Argentiferous Grey Copper Ore (Silber fahlerz), 10 to 30 per cent. Silver. 3. Spaniolite (Quecksilber fablerz), .... 7 to 1 6 per cent. Mercury. The Grey Copper Ore found in the Cornish Mines is very valuable as an ore of Copper, but is rarely argentiferous ; the most valuable of the argentiferous ores are found at Freiberg, and other parts of Germany ; while the mercurial varieties are known in Hungary and several parts of the Tyrol. T. Ruby Silver. This ore is found in crystals, of the rhom- bohedric form, and hexagonal ; its lustre is metallic or semi-me- tallic ; colour black, sometimes approaching cochineal red ; frac- ture conchoidal. It is a double sulphuret of antimony and silver, analogous in composition to the Grey Copper Ore, but much less complex ; its composition is Six atoms of Sulphur, ... 96 ... 17.7 per cent One atom of Antimony, . . . 122 . . . 22.5 Three atoms of Silver, . . . 324 . . . 59.8 ,, 542 100.0 THE NATIVE ELEMENTS. 93 Ruby Silver is found associated with cole spar, native arsenic, and galena, at Andreasberg, in the Hartz ; in Mexico it is worked extensively as an ore of silver, and is not uncommon. U. Light Red Silver. This mineral is closely related to Ruly Silver, differing from it in the fact that arsenic replaces the anti- mony ; it is rhombohedric and hexagonal in crystallization ; lustre adamantine ; colour cochineal red to aurora red ; subtransparent ; fracture conchoidal, uneven. It has the following composition : Six atoms of Sulphur, ... 96 ... 19.4 per cent. One atom of Arsenic, ... 75 ... 15.1 Three atoms of Silver, . . . 324 . . . 65.5 495 There are many other double sulphurets, or sulphur salts, as they are called, known to mineralogists, but not of much impor- tance in practice. One of the most beautiful of these is Bourno- nite, which is a sulphuret of antimony, combined with a sul- phuret of copper and lead ; and there seems to be no limit to the number of antimonio-sulphurets and arsenio-sulphurets that may have been formed by sublimation, and mutual decomposition, under favourable circumstances in lodes. The combinations al- ready described will, it is hoped, give the learner an introduction to the important subject of metallic sulphurets. 20. The Native Elements. Many of the simple bodies known to chemists occur in the Mineral Kingdom perfectly pure, and are called "native" by mineralogists. Among the native elements, the noble, or imperfectly oxidisable metals, are commonly found ; and also elements, as sulphur and carbon, that in their pure state, are probably the result of mutual chemical decomposition of complex bodies, either mineral or organic. A. Native Gold This metal always occurs native; it is monometric, and found chiefly in octahedric and dodecahedric 94 ELEMENTS OF NATURAL HISTORY crystals, and in pyramidal cubes (Figs. 4, 5, 9, 1 1) ; its physical characters are so well known as to render description unneces- sary. Native Gold always contains some silver, up to 10 per cent., and frequently copper, mercury, and iron. It is found in alluvial detritus, spread over many countries in gravel, either in "grains" or in "nuggets," and is separated from the surrounding rock, mechanically by washing, and chemically by amalgamation with mercury, which possesses the property of dissolving gold. In ancient times gold was found probably in the detritus of most countries, but its occurrence is at present confined to the diluvial drift of countries, like California, Australia, &c., in which the earlier inhabitants were not sufficiently civilized to have learned the art of working it, from its original deposits. When gold oc- curs in metalliferous lodes, it is generally associated with iron pyrites, and it is not improbable that all the gold now usually found in gravel beds existed originally in lodes of iron pyrites. B. Native Platinum. This metal is monometric, and has been found, though rarely, in cubes (Fig. 2) ; it is generally com- bined with iron, iridium, and other metals ; it is found in alluvial gravel, like gold ; and was originally discovered in Brazil, where it received its name, platina, the diminutive of plata (silver) ; in the Brazils, it is associated with iridium, rhodium, osmium, pal- ladium, gold, copper, and chromium. It was subsequently found by the Eussians, in large quantities, in the Ural Mountains, and was used by them for some time in the manufacture of coins. When platinum contains much iridium and palladium, as is fre- quently the case, it is called by mineralogists platiniridium, which occurs sometimes, like pure platinum^ in cubes with trun- cated angles. C. Native Quicksilver. Mercury is often found in small fluid globules scattered through the matrix in which cinnabar is found ; it is always the result of the decomposition of this mine- THE NATIVE ELEMENTS. 95 ral, probably by the intervention of organic substances. It is called monometric, because it freezes at 39 below zero into octa- hedric crystals. Mercury forms, with native silver, a mineral called Amalgam, containing two atoms of mercury to one atom of silver ; and occurring in crystals which are modifications of the rhombic dodecahedron. D. Native Silver. This metal is sometimes found native, and is then believed to be produced by a metamorphic reducing agency, influencing the sulphurets or other ores of silver ; it is monometric, and usually found, like the corresponding mineral, native copper, in filiform or arborescent masses, or plates filling natural planes in the matrix. E. Native Copper. This mineral is generally octahedric, or in pyramidal cubes, when it occurs in crystals, and is commonly found in arborescent or flattened masses, like native silver. This remarkable mineral has been found in large masses in serpentine and trap rocks, in Cornwall at the Lizard, and on the shores of Lake Superior at Point Keweenaw. In addition to the native metals already mentioned, the fol- lowing have been found frequently : F. Native Iron. In meteoric masses, associated with Nickel. G. Native Lead. Formed by desulphuration of Galena. H. Native Tin. Associated with gold in Siberia. I. Iridosmium. Alloy of indium, and osmium. K. Native Tellurium. Found in Hungary with gold. L. Native Bismuth. Found with ores of silver, cobalt, &c. M. Native Antimony Associated with silver ores. N. Native Arsenic. Found with antimony, iron, silver, gold, and bismuth. 0. Native Sulphur. This substance is found in trimetric crys- tals, usually pyramidal, and clustered together in cavities ; or in fibrous radiating masses. Sulphur is found as an accessory in rocks, and as a separate 96 ELEMENTS OF NATURAL HISTORY. formation in beds. It is formed directly by sublimation in the fissures of volcanoes, and in the neighbourhood of burning coal beds. It is generally, however, formed by the desulphuration of metallic sulphurets, or of sulphuretted hydrogen in springs. It is remarkable that the artificial crystals of sulphur formed by the chemist, are monoclinic, while the natural crystals are always trimetric. P. Native Carbon. This element is found "native" under three different forms, as Diamond, Graphite, and Anthracite. (a.) Diamond. Occurs in the monometric system, frequently in the forms of the six-faced Octahedron, or Tetrahedron (Figs. 13, 14), with curved faces and edges ; it has a watery lustre, but is occasionally tinged yellow, red, orange, green, brown, or black. The diamond consists of pure carbon crystallized, and it is remarkable that Newton conjectured, from its high refractive power, that it was combustible ; it is totally consumed at a high temperature (14 of Wedgwood's pyrometer), and converted into carbonic acid gas. It is usually found in regions that furnish a laminated, talcose, sandstone rock called Itacolumite, from the name of the locality in Brazil where the connexion between this matrix rock and the diamond was first noticed by mineralogists. Itacolumite sometimes passes into flexible sandstone, and has been found in the Brazils, in North Carolina, in the Ural, and near Delhi in Hindustan. There is little doubt that the diamond in all cases is formed in a sandstone rock resembling Itacolumite, and that it owes its existence to organic causes. It is generally found loose in the soil, having been washed, by atmospheric agency, from its original nidus in the sandstone rock. The diamonds found in the Brazils are associated with gold, platinum, magnetic iron, and rutile. In the Ural workings the diamonds are found associated with gold. In India, diamonds are found in sandstone between Hyderabad and Masulipatam, where the famous Kohinoor was produced. DIAMONDS. 97 Diamonds areusually weighed by carats (3^ grs.), and increase in value enormously with increase in weight. The following may be mentioned as instances of remarkable diamonds : The largest diamond of which we have any record is that de- scribed by Tavernier as belonging to the great Mogul. It was found A. D. 1550, in the mine of Colone, and, in its rough state, weighed 900 carats, but was reduced in cutting it to 272! carats. The Kohinoor, or " Mountain of Light," became the property of the Queen of England on the annexation of the Punjaub in 1850. It is reputed to be 4OOO x years old ; and it is certain that in 50 A. c. it belonged to the Rajah of Mjayin, and remained in the possession of his successors until the Mahomedans conquered India. The Kohinoor is mentioned by Tavernier A. D. 1665, as the property of the Great Mogul. Its original weight , was 793 carats, and it has been reduced by repeated cuttings to its present weight, which is only 103! carats. It is thought that the original rough form of the Kohinoor was that of a rhombic dodecahedron (Fig- 1 1), and that this great mass was broken ac- cidentally into three parts, forming the Kohinoor, the Russian diamond, and the Dorianoor, or " Ocean of Light." The Russian diamond weighed 1 94 carats, and was sold for 90,000, and an annuity of 4000. The Kohinoor and Dorianoor formed part of the plunder seized by Nadir Shah, at the taking of Delhi in 1739, when the treasures carried off exceeded 70,000,000 in value. (b.) Graphite, or Plumbago. Occurs in the hexagonal system, usually in six-sided, thin tabular, or short prismatic crystals; also massive, in radiated, lamellar, or compact aggregates; colour iron black to grey ; streak black, with metallic lustre ; soils paper ; used for pencils to draw and write with. It consists of carbon, with some iron in combination as a carburet of iron. Graphite is sometimes found, as in Eastern Siberia, forming beds in the metamorphic crystalline rocks, and is believed to be 98 ELEMENTS OF NATURAL HISTORY. the result of the metamorphosis of coal beds. It also occurs as an accessory in the trap rocks, as at Borrowdale, in Cumberland ; and in gneissose beds in Greenland. (c.) Anthracite. This term expresses the varieties of coal that do not contain bitumen. All coal beds are the product of vegetation, and are formed in the localities where the plants grew. Coal consists principally of carbon, with more or less of bitumen, and a small quantity of silica and alumina, and sometimes peroxide of iron ; potash and soda have been frequently found in it, and are, no doubt, the remains of the alkaline salts of the growing plants. The varieties of coal that contain bitumen are the following: (o / .) Pitch, or Caking Coal, burns with a yellow flame, and re- quires frequent stirring to prevent its caking ; colour velvet, or greyish black. (i'.) Cherry Coal; burns more rapidly than pitch coal, and being more brittle, breaks up readily, so as to require less stir- ring. (c'.) Splint Coal; is a hard and dry kind of cherry coal, passing into cannel coal. (a".) Cannel Coal ; has a dark greyish black or brownish black colour ; a large conchoidal fracture, and takes a good polish. It burns with a clear yellow flame, without melting, and has been used as a substitute for candles, from which cir- cumstance it derives its name. (e'.) Jet ; resembles cannel coal, but is blacker, and has a more brilliant lustre. It is found in detached pieces in clay, near Whitby and elsewhere. Jet was called Gagas by the an- cients, from the name of a river in Lycia, at the mouth of which it was found, and many virtues, medicinal and other- wise, were attributed to it. Anthracite has a bright, submetallic lustre; iron black colour, often iridescent ; it is opaque, and has a conchoidal fracture ; no ORGANIC COMPOUNDS. 99 varieties of coal are called anthracite that contain less than 90 percent, of pure carbon. Anthracite occurs in many coal beds, especially in Pennsylvania, South "Wales, Leinster, and parts of Saxony and Russia. 21. Organic Compounds. Among the mineral substances, whose origin is clearly organic, the following may be noticed : A. Bitumen. This has been already mentioned as forming the chief distinction between ordinary coal and anthracite. Many different oily and pitchy substances are included under the term bitumen, of which the most important are naphtha and as- phalte. (a.) Naphtha. A volatile and colourless oil with bituminous smell ; it is frequently mixed with paraffine and other sub- stances, especially asphalte ; when quite pure, its composi- tion is as follows : Six atoms of Carbon, .... 36 ... 88 per cent. Five atoms of Hydrogen, ... 5 ... i a 41 100 (.) Asphalte. This may be described as a hardened mineral pitch, not containing oil ; it is massive, and has a conchoidal fracture ; colour pitch black ; opaque, lustre resinous ; when rubbed, gives out a bituminous odour ; is easily ignited, and burns with a bright flame and thick smoke. Naphtha, under the name of Hock oil, is found in natural wells in many places ; as Persia, Pennsylvania, Canada ; where it is be- lieved to impregnate the sandstones and other rocks in which it is found, in consequence of its natural distillation from coal beds, by virtue of subterranean heat. Asphalte, or mineral pitch, is found, under similar circum- stances, in the Dead Sea, in Trinidad, and elsewhere. It is also found in limestones in Ireland and other countries, as the result of the destructive natural distillation of fossil shells, and even in H 2 100 ELEMENTS OF NATURAL HISTORY. granites, as at Poldice, in Cornwall ; and in a bed of gneiss, thirty yards thick, at Nullaberg, Sweden. It is said, also, to have been detected in meteoric stones. B. Amber. This mineral is found under circumstances simi- lar to those under whichy^ is worked, in rounded masses in clay ; with, frequently, insects and fragments of plants enclosed in them ; it has a yellow colour, with pencillings ; lustre resinous ; is translucent or transparent, and becomes electric on being rubbed. It has the following composition : Ten atoms of Carbon, ... 60 .... 83.3 per cent. Four atoms of Hydrogen, . 4 . . . - n.i One atom of Oxygen, . .V. 8 .... 5.6 ,, 72 100.0 Amber is a fossil gum resin, produced by conifers of the ter- tiary period ; it is found in the upper chalk beds of Lemberg, and in pebbles washed from the tertiary beds on the south shore of the Baltic, and the coasts of Yorkshire and Essex. C. Mellite. This mineral, also called Honey stone, occurs in dimetric crystals, pyramidal, and imbedded singly in crystals having the form shown in Fig. 1 9 ; colour, honey yellow to wax yellow ; seldom white ; lustre resinous ; semitranslucent. Mellite is an hydrated compound of an organic acid, called mellitic acid, with alumina ; and mellitic acid itself is composed of four atoms of carbon and three atoms of oxygen (i. e. equal parts of both). Mellite has the following composition : Three atoms of Mellitic Acid, . 144.0 . . 40.3 per cent. One atom of Alumina, ... 51.5 .. 14.4 ,, Eighteen atoms of Water, . . 162.0 . . 45.3 357.5 100.0 Mellite occurs frequently in lignite, or brown coal ; and is found in Moravia, Thuringia, Bohemia, and Greenland. PAET II. THE VEGETABLE KINGDOM. " VEGETABILIA Corpora organisata et viva, non sentientia." " Regnum Vegetabile vivens superficiem vestit, radiculis bibulis ter- rena haurit ; foliis obvolitantibus aetherea respirat ; calida metamorphosi declarator in festivales nuptias generantes dispergenda intra praescriptas stationes semina." Linnceus. CHAPTEE III. ORGANS OF PLANTS. MINERALS, according to the famous definition of the greatest of all naturalists, are " corpora congesta;" whereas plants are "cor- pora organisata et viva? The mineral possesses a definite shape and definite chemical composition, and simply grows by the aggregation of particles of the same kind continually added from without ; the plant, on the other hand, possesses organs and life ; all its parts are not of the same kind, some being appropriated to one use and some to another ; and it possesses life ; or has a com- mencement and a termination of its individual existence, during which it produces other living things, which survive it, and perish in their turn, having previously produced others to take their place, and hand on to futare ages the representatives of the individual. It is necessary, therefore, to the complete study of plants, that we should understand their organs, and study their life. The description of the organs of plants is called vegetable 102 ELEMENTS OF NATURAL HISTORY. anatomy, or organograpJiy ; and the study of these organs in action, or in their living state, is called vegetable physiology. These two subjects, together with a brief account of the clas- sification of plants, will be sufficient for an elementary trea- tise. i. The Plant Type. If we inquire into the history of any tree or plant, we shall find some such record as the following : A seed, produced by some pre-existing tree or plant, was placed in the ground, and commenced to grow, by pushing downwards into the ground a radicle or rootlet, and pushing upwards into the air, one, two, or more seed leaves, or cotyledons;* from the axis, or intersection of these seed leaves, the ascending stem of the plant continued to grow, throwing out fresh leaves in its ascent, and also branches ; at the same time, the root descending into the ground, threw out other rootlets ; and repetitive this process, characteristic of vegetation, was continued until the small seed had grown into the giant tree, spreading out its myriads of arms, covered with leaves, and piercing the ground beneath by roots and rootlets sufficiently strong and extensive to form an anchorage power to prevent the tree from falling, either by its own weight, or in consequence of the pressure of the wind upon its surface. In this process we observe three classes of organs root, stem, leaf. By the roots our plant is held firmly in the ground, and sucks up nourishment from the salts and organic matters dissolved in the moisture that surrounds them. The leaves absorb certain gases and give out others into the air, performing the double office of respiring and digesting the matters conveyed to them from the ground. The stem serves the purpose of the great communicating * KoTvXrjSiiiv A cup-shaped organ, like the socket of the hip-joint, or the suckers on the arms of the cuttle-fish. THE PLANT TYPE. 103 organ between the roots and leaves ; it encloses and protects the numerous canals that convey the crude food from the roots to the leaves, and others that reconvey the digested sap from the leaves, to be deposited in the various parts of the plant in which growth proceeds. Our type plant now possesses organs of absorption, respiration, circulation, digestion, and consequently grows by an organic pro- cess, and not as a mineral, by the constant addition of identical molecules by chemical affinities ; but it also possesses the fatal gift of life, and must therefore die, after a period long or short, as the great Creator wills. A mineral never dies ; it may be de- composed and converted into other minerals, but it is continu- ally reproduced again by the action of the chemical and crystalline forces that first produced it. Our plant, however, being a living thing, must die, and its growth must have a limit. The indi- vidual plant only dies, for the type plant is continued by the process of reproduction, which belongs essentially to living things. For this purpose, certain portions of our plant are set apart, which are called flowers, or organs intended for the production of seeds. "When the seeds are formed, the function of the old plant is fulfilled, and sooner or later it perishes, giving place to the younger plants produced from its own seeds ; and these plants in their turn produce their seeds, and die. Such is the lot of all living things, and it seems impossible for us to regard it without sorrow, whether it be that it contra- dicts our own instinctive yearning for immortality, or that our finite faculties cannot comprehend the Creator's wisdom. Our plant is composed of organs of nutrition, respiration, re- production, and its life consists in the suitable exercise of all these functions. The organs themselves are the roots, the stem, and branches, the leaves, and the /lowers, and these compound organs are themselves composed of molecular elements and tissues which must be first described. 104 ELEMENTS OF NATURAL HISTORY. 2. Cellular Tissue. A microscopic examination of the minute structure of plants shows us that it is ultimately composed, either of rounded ellipsoidal cells, or of elongated fibres, which are closed vessels, and form the ultimate molecules of a plant. The cells are shown in Fig. 34, and the fibres in Fig. 35. The whole structure of young plants, and Fig. 34- Fig. 35. of mosses and other vegetables of the lowest grade, even when full grown, is made up of cellular tissue; but this fabric is too tender and brittle to give the needful strength and toughness to large plants, in which, therefore, it is always more or less replaced by woody fibre, which, from the elongated form of its elementary cells, and the superior toughness of the lignine of which its cell walls are composed, is better calculated to form the frame work of the stems and branches of the larger plants and trees. The cells of which the young plant is composed have the power of subdividing themselves, so as to form two cells out of one, each cell having its enclosing wall complete ; and it is by this process that growth is carried on, each cell that is so pro- duced being capable, up to a certain limit, of again subdividing, and of growing in bulk. Thus, vegetable growth consists essen- tially of two things : CELLULAR TISSUE. IOC (a.) The expansion of each cell, until it reaches its full size, which is generally ^^th of an inch in diameter. (b.} The multiplication of the cells in number, by the mysterious process of fission or subdivision, which continues as long as the plant grows. The cells, as they grow, build up the tissues or fabric of the plant, which is thus ultimately composed of minute closed sacs filled with various fluid or semifluid substances ; and if the cells were not capable of changing their shapes by mutual pres- sure, there would occur in the plant a number of intercellular spaces or vacuities, as in a pile of cannon balls, the total volume of which might bear a very sensible proportion to the space filled by the cells themselves. We find, however, that the cells in contact behave like a number of soap bubbles, and form plane walls dividing them from each other, like the cells of bees. This appearance is shown in Figs. 36, and 37 ; in the former of which Fig. 36. Fig. 37. it will be observed that a pentagonal structure predominates, and in the latter, an hexagonal. If the cells were originally perfect spheres, and altered in shape by mutual pressure, they would always take on the forms of some one or other of the five Euclidean solids ; and, accordingly, we observe in the cells of plants, under the microscope, in many cases, the tetrahedron, Fig. i ; the cube, Fig. 2 ; the dodecahedron, 106 ELEMENTS OF NATURAL HISTORY. Fig. 6 ; but never, so far as I know, either the octahedron or the icosahedron. When the cells, as often happens, are cylindrical in form, instead of spherical, their mutual pressure produces hexa- gonal forms, as in Fig. 37, which are terminated, sometimes as in the figure, by flat ends, and sometimes by rhombic trihedral extre- mities; in this latter case, the cell assumes the shape of the rhombic dodecahedron (Fig. u). The intercellular spaces are generally small, as compared with the whole mass of cellular tissue ; but they sometimes form regular tubes or air passages, as shown in Fig. 38, and may be Fig. 38. compared to chimneys placed in stacks, and formed of cells in- stead of bricks. Such air passages are commonly found on cutting across the stems and leaves of marsh and aquatic plants. The size of cells in plants varies from ^th to yoVo^ ^ an inch in diameter, the ordinary size being -j^th, so that there may be 100 millions of cells in a cubic inch. The walls of cells are at first thin, and always colourless, but in many cases they become thicker by additions made continually on the inner side, and this process sometimes continues until the cell becomes per- fectly solid. The cells while young and living are always closed, some parts of their walls being, however, thinner than others, but there are no actual pores opening from one cell into the others ; and yet the sap and all the juices of the plant are readily carried up and down, from one end of the plant to the other, by means of these closed cells, by the action of the molecular forces called endosmose and exosmose, by natural philosophers. WOODY FIBRE. 107 "Whenever two cavities are separated by an animal or vegeta- ble membrane, and contain fluids differing from each other in physical and chemical properties, it is found that the fluids pass from one cavity into the other, according to laws depending on their composition, and especially on their density. Now, the ac- tion of the sun and air upon the leaves of plants tends constantly to alter the density and composition of the contents of the cells exposed to its influence, and so creates a molecular force extend- ing from cell to cell, from the remotest leaf down to the deepest rootlet of the plant. These molecular forces are found sufficient to cause the ascent of the sap, and to produce the distribution of the concocted juices to every organ of the plant requiring their supply and nourishment. 3. Woody Fibre. Wood cells, shown in Fig. 35, differ from ordinary cells, in their elongated fusiform shape, and in having thicker walls ; and, from their shape, they admit more readily than spheroidal cells of intercellular spaces, which in woody fibre are called ducts, or vessels. Wood con- sists of bundles of woody fibre, and of ducts variously intermingled, which run lengthwise through the roots and stem, and terminate in the veins of the leaves. In wood cells, the thickening of the wall takes place from the inner side, ac- cording to regular laws, certain spots or pores, placed opposite each other in the adjoining cells, not being thickened, but retaining their original coating, through which the sap and juices pass from cell to cell. This structure is shown in Fig. 39, which requires no further explanation. It must be remembered, that the wood cells do not form a connected system of pipes opening into each other, so as to convey an unbroken stream ** 39- of sap through the plant. The sap is compelled to ascend from 108 ELEMENTS OF NATURAL HISTORY. cell to cell, by small molecular forces, so that in mounting through a single foot it has often to pass through upwards of 2000 par- titions. The regular canals or ducts found in the intervals of woody fibre are formed by the fusion of perpendicular rows of cells placed end on, which, by the absorption of their terminating walls, become converted into continuous tubes of more or less considerable length. These vessels or ducts are variously marked on their inner surface, and have received names from botanists, depending on these marks, the uses and origin of which are very imperfectly known. The following kinds of ducts are recog- nized : (.) Spiral Ducts. Represented in Fig. 40. (b.) Reticulated Ducts. Shown in Fig. 41. (0.) Annular Ducts. Fig. 42. (d,} Scalariform Ducts. Fig. 43. (e.} Dotted Ducts Fig. 44. These are the ducts most com - Fig. 40. Fig. 41. Fig. 42. monly found in the woody tissue of Exogenous plants ; and they are DUCTS AND VESSELS. 109 marked by pits or dots, in the same manner as the wood cells shown in Figs. 35 and 39. Fig- 43- Fig. 44. Spiral vessels are found in the youngest parts of the plants in which they occur; and are abundantly developed in young woody tissue, and in the petals of flowers. Annular vessels pass frequently into the former, and gene- rally occur later, and in the same situations. This is the com- monest form of vessel in the Equisetacea. Reticulated vessels occur in succulent roots, stems, and petioles of Endogenous plants, and are generally of large size, as compared with other classes of ducts. Scalariform vessels are especially characteristic of the woody tissue of Ferns and Clulmosses, and are generally altered into hexagonal tubes by the lateral pressure of the surrounding cells. 4. The Seed. The ancient maxim, omne vivum ex ovo, applies to plants as well as to animals ; we place a seed in the ground, it grows up into a tree, bears flowers and fruit containing seeds like the original, and then dies, allowing its likeness or type to be perpetuated by the seeds it has formed. The circle is com- plete, commencing and ending with a seed ; and we may obtain the simplest and clearest idea of plant life, by studying it from the seed placed in the ground, through all its modifications and no ELEMENTS OF NATURAL HISTORY. changes, until we arrive at the formation of the fresh seeds, which are to recommence the process of germination once again. If we examine, in spring, the germinating seed of mignonette, or other plant used for the experiment ; we shall perceive that it throws up into the air two tiny seed leaves, mounted upon a little stem, having little rootlets at its extremity ; and, upon moistening and opening a seed itself, we can easily recognize that this tiny plant pre-existed, folded up in the seed from which it sprang. The very first step, therefore, in vegetation, consists in the simultaneous production of three organs a root, a stem, and leaves. The leaves so produced are called seed leaves or cotyledons, and 45- Fig. 46. Fig. 47. plants are classified according to important varieties occurring in their seed leaves. 1. Monocotyledons (having one seed leaf), Tig. 45. 2. Dicotyledons (having two seed leaves), Fig. 46. 3. Polycotyledons (having many seed leaves), Pig. 47. 4. Acotyledons (having no seed leaves), Fig. 48. COTYLEDONS. Ill The rudimentary plantlet contained in the seed is called an ernbryon ; its little stem is called the radicle, its seed leaves are called cotyledons, and the little bud of undeveloped leaves at its summit is called the plumule. Thus the plant, a few days old, is an epitome of the tree or herb ; it has a stem, from the lower end of which roots strike downwards : it has leaves, which perform the office of digestion and respira- tion ; and it has a stem, which expands upwards, forming new leaves to continue the offices of digestion and respiration on a scale suited to the increased size of the organism. At its first commencement of growth, the young plant derives its nourishment from the fleshy substance of the cotyledons, or from other stores of albuminous food laid up in various parts of the seed ; but becomes capable of providing for itself, as soon as the cotyledons have assumed the form of green leaves, or as soon as the budding plumule has developed such : for now the rootlets derive mineral nourishment from the ground, which is carried by the ascending sap into the leaves, where it is digested by the action of air and light, and forms the material from which fresh cells are formed and growth continued ; and as soon as this stage is reached the seed leaves die, Having finished their task, and the plant enters upon a new stage of its existence, deriving all its nourishment from the ground, and elaborating it into higher forms of matter, by the joint influence of light, air, and life in its leaves. The food stored up for the young plant in the cotyledons was likened by the older botanists to the yolk of an egg, while that stored up in the mass of the seed, around the embryon, but not forming part of its substance, was compared to the white of the egg. 5. Buds. There are many trees, shrubs, and herbs, whose whole life consists in a repetition of the process of growth just 112 ELEMENTS OF NATURAL HISTORY. described. The stems of such plants rise by a simple shaft, car- rying a terminal bud on its extremity, by the continued evolution of which the plant grows, as it originally grew from the plumule of its seed. Some Exogens, such as Cycas, and many of the En- dogens plants grow in this fashion, the Yucca, the Cocoa nut palm, and the Banana; these are shown in Fig. 49. Fig. 49. (a.) Cycas. (c.) Cocoa nut palm. (6.) Yucca. () ; this is the portion of the bark that acquires so great an importance in such trees as the Cork oak, Elm, and others. At the close of the first season of growth, the cross section of the branch presents the following structures, counting from within, outwards (Fig. 59) : 1. The pith cellular tissue. 2. The medullary sheath spiral ducts. 124 ELEMENTS OF NATURAL HISTORY. 3. The woody zone woody fibres with ducts, annular and dotted. 4. The liber bass fibres. 5. The middle bark cellular tissue. 6. The Corky layer flattened cellular tissue. 7. The Epidermis flattened cellular tissue with stomata. In addition to these structures, placed round each other in rings, the medullary rays form radiating, vertical sheets of cel- lular tissue connecting the pith and bark together, and forming the silver rays so conspicuous in the cross section of certain woods. Let us now examine what occurs at the commencement of the second year of growth. It is found that the border ground, lying on the outer side of the woody zone, and the inner side of the liber, has become filled with a highly digested mucilaginous sap, con- taining all the elements proper for the formation of new cells and fibres, and called plastic sap, or Cambium, by the older botanists. This concocted sap corresponds to the plastic lymph of animal physiologists, and contains much dextrine ; and as soon as the stimulus of returning spring is applied, it commences to lay down a fresh zone of woody fibres, abundantly provided with spiral vessels on the inner side, while the medullary rays are either prolonged by the addition of new cellular tissue, or new rays are formed to keep up the vital connexion between the pith and bark. Thus the wood grows, year by year, forming a fresh ring or zone each season, so that the age of a branch may be ascertained by counting the number of such rings or zones of which it is com- posed. The inner bark, or liber, like the woody zone, continues to grow during the life of the tree, by yearly additions made to its inner surface each spring, from the cambium ; and sometimes a cross section of the liber shows rings of growth as regular as those of the wood; but, more commonly, the successive deposits of liber are undistinguishable from each other. GROWTH OF EXOGENS, 125 The middle bark, composed altogether of cellular tissue, does not increase generally after the first year, and being shut out by the corky layer from the light, often quickly perishes, never to be renewed. The outer bark, or corky layer, increases by the addition of tabular cells, for a few years, by additions made upon its inner surface ; and in some trees, as the Paper birch, fresh layers of corky bark are added for many years, which readily exfoliate when dead, and give the tree its name. From what has been already stated, it appears that in Exogens the woody central stem grows by additions made each season to its outer side, from the cambium cells, while the bark grows by additions made yearly from the cambium to its inner surface. The inner and older parts of the wood become thus, year by year, further removed from the active and living part of the stem, which is found chiefly in the cambium zone. For some time a vital connexion between the outer and inner woody layers is maintained by the medullary rays ; but these become gradually choked up, together with the vessels of the older wood, by mine- ral matter imbibed with the water by the roots, and by the gradual thickening of the woody fibres, and consequent diminu- tion of their internal capacity. The older zones of wood thus grow harder and darker in colour, and receive the name of heart- wood (duramen), while the newer and still bibulous layers of the outer zones are called sapwood (alburnum), and continue to carry from the rootlets to the leaves the crude sap, which is there di- gested, and then sent down through the vessels of the liber, to form the plastic cambium, from which the new cells, both of the woody stem and of the fibrous liber, must be produced. The outer part of the bark, exposed to atmospheric and me- chanical agencies, soon loses its vitality, and becomes as dead as the heart wood itself, so that in time the only living parts of an Exogen are 126 ELEMENTS OF NATURAL HISTORY. (a.) The summit of the stem and branches, with the buds that prolong them upwards and outwards, and develope leaves each year for the respiration and digestion of the tree, (i.) The fresh tips of the rootlets pushed forwards into the ground, from which they imbibe the mineral and organic food, which must be conveyed to the leaves for concoction, (c.) The outermost zone of wood, that carries the crude sap to the leaves ; and the innermost zone of bark, that reconveys from the leaves the digested sap, to fill the cambium cells. Thus it appears that the inner heart wood and pith of a tree may rot and die, and that the outer bark may also be destroyed or die ; and yet that the tree will continue to live on, provided its cambium zone be uninjured, from which are produced, year by year, the additions made to the outer circumference of the wood, and to the inner circumference of the bark. B. Endogens. If we examine with a microscope the cross section of one of the wedges of young woody tissue, formed in the branch of a growing Exogen (Fig. 58), we shall find it to be com- posed, as shown in Fig. 59, from within, outwards, of the fol- lowing tissues : 1 . Woody fibres, containing spiral vessels. 2. Woody fibres, containing dotted and annular vessels. 3. Woody fibres, longer and thinner than the others, forming the bast fibres, characteristic of the inner bark. These wedges of variously constituted woody fibre are placed in rings or zones around a central pith of cellular tissue, and are sur- rounded by an exterior zone of cellular tissue, which forms the ex- ternal bark, destitute of woody fibres. The elementary bundles of fibro-vascular tissue, which are arranged in wedge-like masses round a common centre in the Exogens, are, in the Endogens, plunged as if at random, through the mass of cellular tissue of the stem is composed. In Fig. 60 is shown the vertical STEM OF ENDOOENS. I2 7 section of an Endogen, or monocotyledonous plant, such as the common cane ; and in Fig. 61 is shown the magnified section of Fig. 60. Fig. 61. one of the fibro- vascular bundles of woody fibres that penetrate the cellular tissue of the stem in a vertical direction. These ele- mentary bundles are always placed, with reference to the centre of the stem, in the same relative position as the regular wedges of woody tissue in the Exogens ; that is to say, the spiral vessels are found in the woody tissue on the inner side, the dotted and annular ducts in the centre, and on the outer side occur the slender bast fibres, characteristic of the liber or woody bark of the Exogen. Instead, however, of being symmetrically arranged in zones of wedges, so as to form woody rings on the inner side, and a continuous bark on the outer side, as in the Exogens, these elementary bundles of woody fibre are unsymmetrically placed, and no regular bark surrounding the entire stem can be formed. The monocotyledonous plants were called Endogens byDaubenton, from an erroneous idea as to their mode of growth, which he conceived to take place in a manner the converse of the growth of Exogens. His idea of endogenous growth is illustrated by Fig. 62, which' represents the fibro- vascular bundles rising inside each other at the centre, and promoting the growth of the tree, iz8 ELEMENTS OF NATURAL HISTORY. \ like the sliding tubes of a telescope. According to this idea of the growth of an Endogen, the density of the outer layers of the cross section of an Endogen is due simply to mecha- nical pressure, caused by the continued central evo- lution of new shoots to prolong the tree, and it is difficult to conceive how the young fibro-vascular bundles at the centre could be themselves protected from that pressure. The cross section of the lower part of the stem of a cane or palm (fig. 63) shows near the outer circumference a zone of darker coloured and more thickly rig. 6 2 . set vascular bun- dles than can be accounted for by simple excentric pressure; for this dense zone is often separated from the outer rind by another zone shown in the figure, in which cellular tissue (parenchyma) preponderates above the woody bundles as much, as it does in the central portions of the stem. If the density of the outer zone were simply due to mechanical pressure, the most dense portion of the stem should be that nearest the rind, which is not always the case, although it is sometimes so. A careful examination of the course of the fibro-vascular bun- dles of Endogens led the botanist Mohl to the more correct view of their structure, shown in Fig. 64. The woody fibres are formed in all plants from the leaves, which send down the digested sap con- taining the plastic cambium, which deposits the new fibres and cells ; and the course of these bundles of fibres in Endogens is, at first, towards the centre of the stem, producing the appearance GROWTH OF ENDOGENS. 129 that misled Daubenton ; but when their course is followed still further down the stem, they are found to diverge, much more slowly than they originally converged, until theyul- s^ss*.. timately reach the dark superficial zone shown in Fig. 63, where they either terminate in the rind, or false bark, or disappear altogether. One of the largest vegetables on the globe is the Dragon tree of the Canaries (Draccena Draco), allied to the Asparagus and Lily. It grows near Orotava, in Teneriffe, and in 1799 was found by Humboldt to measure 45 ft. in circumference (14^ ft. diameter). The great size of this enormous tree is mentioned by many of the older writers; and as early as 1402, it is described by Bethencourt, as large, and as hol- low as it is now. Humboldt considers this particular Dragon tree and the Baobab of Senegal, described by Adanson, as the oldest plants now living. This Baobab is an exogen, and measures 78 ft. in circum- ference, and is considered by botanists to be 5000 years old (be the same more or less !) The Dragon Fi S- 6 4- tree of the Canaries is hollowed out into a Lady Chapel, while the Baolab is excavated by the negroes as a place of sepulture for criminals, who are speedily converted into mummies by the dry, soft wood of which the trunk is composed. It is worthy of remark, that the destruction of the interior of an endogen, without injury to the tree, effectually disposes of the old theory of its mode of growth, and proves that, like an exogen, its living parts consist of the new rootlets, the fresh leaves, and the vessels and ducts that carry the ascending and descending sap. The true distinctions between the stems of monocotyledonous and dicotyledonous plants has never been better stated than by Desfontaines, who was the first to point out the difference be- tween them. He says : ELEMENTS OF NATURAL HISTORY. Plants may be divided into two great classes, according to the structure of their stems. j . Those that have no distinct concentric zones, whose density decreases from the circumference towards the centre, and whose pith (cellular tissue) is interposed between the fibrous bundles without diverging medullary rays ; these are the monocotyledons. 2. Those that have distinct concentric zones, whose density decreases from the centre to- wards the circumference, whose pith is contained in a longitu- dinal canal with diverging me- dullary rays ; these are the di- cotyledons. C. Acrogem. These are acotyle- dons possessing fibrous woody tissue in their stems, by which they are distinguished from the thallogens, which consist altogether of cellular tissue, and have no stems properly so called. The most remarkable aero- gens, are the Tree ferns of tropical climates, one of the most beautiful of which is shown in Fig. 65, which represents the Alsophila of the East Indies, which grows to a height of fifty feet. Amongst our own plants, acrogens are well represented by com- mon ferns and club mosses (Lycopo- diacece). In the structure of their stem, acrogens are readily distin- guished from endogens and exogens. Fig. 6 5 . S TEM OF A CROGENS. 1 3 1 The typical structure of the stem may be understood from Fig. 66, which is the cross section of a tree fern ( Cyalhea) from the "West Indies. The woody fibro-vascular bundles (prosenchyma} form somewhat sym- metrically shaped masses, which are placed in a single ring, surrounded by the pith or cellular tissue (paren- chyma) that fills the remainder of the stem. The outer part of these bun- dles of prosenchyma is formed of woody fibres, shaded dark ; and the central portion, more lightly shaded, g * is occupied by woody fibres and vessels, which are always reticu- lated (Fig. 41), annular (Fig. 42), or scalariform (Fig. 43) ; and rarely spiral (Fig. 40), or dotted (Fig. 44). The reasons for these peculiarities in the vessels of plants are not known, but the fact itself is well established. The outer rind, or false bark, of the acrogens, is formed of the decayed leaf scales that belong to the leaves of past seasons. The peculiar structure of an acrogenous stem may be studied by cutting across the lower part of the stem of the common Brake fern (Pteris aquilina], in which the dark lines forming the outer margins of the fibro-vascular bundles produce the appearance called by schoolboys "King Charles in the Oak." Acrogens, like endogens, grow by a bunch of young leaves, formed each season at the top, and like them possess a constant thickness of stem ; for it is a physiological law in botany, that the thickness of a stem is in direct proportion to the area of foliage ; hence in exogens, as the foliage increases year by year, the stem must in- crease also ; whereas in endogens and acrogens, as the surface of the foliage is always constant, the section of the stem must be also constant. K 2 132 ELEMENTS OF NATURAL HISTORY. D. Thallogem. These plants, like the acrogens, are acoty- ledons (Fig. 48), but they are still lower in their organization than acrogens, for throughout their whole life they consist of cellular tissue only ; and although some of them, as the Mosses, simulate the aspect of the higher orders of plants, hy the ap- pearance of a stem and roots, yet these organs never contain any woody fibres or vascular tissue, and their life consists in the im- bibition of mineral matter by endosmosis ; its elaboration within the cells by a process of digestion, which in the higher plants is assigned to special organs, or leaves ; and in the reproduction of young cells by a process of internal generation, or fission, very inferior to that found in higher plants, where the function of re- production is assigned to a special class of organs, called flowers. The principal plants referred by botanists to the class of thallogem are Mosses, Liverworts, Funguses, Seaweeds, and Lichens ; together with the still lower forms consisting of single cells, such as Desmids and Diatoms. 9. The Leaf. Leaves do not grow at random upon the stem of a plant, but at regular intervals according to certain laws, the symmetry of which resembles that of the laws that govern the production of crystals, in the mineral kingdom. The law of the production of leaves is called phyllotaxis (0vXXoTafts), and is of two kinds alternate and opposite. A. Alternate Leaves. Leaves are said to be alternate, when one leaf only is formed at the same point of the growing stem, and the portion of the stem included between two successive leaves is called an internode ; the point at which the leaf is pro- duced being called the node, because, as has been already shown, a power of forming a bud and branch essentially exists in the stem, wherever a leaf is produced. The simplest case of alternate leaves is that of distichous or two-rowed leaves ; in this case the leaves are placed alternately on opposite sides of the stem, so as to form two vertical rows of leaves exactly opposite to each other. If we number the ARRANGEMENT OF LEAVES. leaves of such an arrangement in the order of their developement, we shall find the two vertical rows to consist of First row, . ist . . 3rd . . 5th . . 7th . &c. Second row, . . 2nd . . 4th . . 6th . . 8th . &c. The distichous arrangement occurs in all Grasses, and in many other endogens, and is sometimes found in exogens. The next simplest case of alternate leaves is that called tris- tichous, which is characteristic of the Sedges, and some other en- dogens. In this arrangement the leaves are placed in three ver- tical rows, as follows : First row, . . . . ist . 4th . 7th . loth Second row, .... and . fth . 8th . nth Third row 3rd . 6th . gth . 1 2th This arrangement is shown satisfac- torily in Fig. 67. The distichous and tristichous arrangements form the basis of the phyllotaxis of almost all alternate leaved plants in the following way. If we write down the vulgar fraction, whose numerator is the number of spires or revo- lutions round the growing stem made by the leaves, before a new leaf is produced vertically over the first leaf; and whose denominator is the number of internodes formed in the same time ; we may repre- sent the distichous and tristichous phyllo- taxis thus Distichous Phyllotaxis, ^ Tristichous Phyllotaxis, \ These fractions signify that in both cases the spiral line traced round the stem joining the leaves in the order of their pro- duction makes only one revolution before we arrive at a leaf placed vertically over '34 ELEMENTS OF NATURAL HISTORY. 25 the first leaf; but that in the first case there are two internodes, while in the second case there are three internodes. The arrangement next to be considered is the dipentastichotis, found by adding the numerators and denominators of the preced- ing fractions together, thus Dipentastichous phyllotaxis, | In this arrangement there are two revolutions of the spiral requisite to produce the leaf vertically over the first leaf, and there are five internodes produced in the two revolutions. It follows from this, that there are five vertical rows of leaves, which, however, are not generally well marked, because the length of the internodes, and the spiral lines generally draw off" the eye from noticing the vertical ranks ; which are, First row, i 6 n 16 21 Second row, 2 7 12 17 22 Third row, 3 8 13 18 23 Fourth row, 49 14 19 24 Fifth row, 5 10 15 20 The dipentastichous arrangement is illus- trated in Fig. 68, and may be readily seen in the Apple, Cherry, or Poplar. The next phyllotaxis of alternate leaves, in ascending order of complexity, is the Trioctasti- chous. Trioctastichous phyllotaxis, . . . . f This is found by adding together the nu- merators and denominators of the tristichons and dipentastichous phyllotaxis ; and it may be well studied in the Holly, the Aconite, or the Plantain. In this case the ninth leaf is placed vertically, over the first, the tenth over the se- cond, and so on ; the spiral making three turns while eight internodes are formed; and the stem showing eight vertical rows of leaves. Other more complex forms are well known, Fig. 68. .3 PB.TLL TA XIS. 1 3 5 which are produced in like manner by the addition of the nume- rators and denominators of the fractions that represent the phyl- lotaxes ; and the whole series is simply summed up in the following fractions, formed from each other, after the first two, by the same rule 112 3 5 8 15 _ 21 2~3~J~5~TT~?T~74"~5T Here we may end the series, for higher combinations have seldom been found to occur in nature. The Houseleek and White pine illustrate the phyllotaxis of -^ ; and sometimes singular differences are found in the phyllotaxis of closely allied species. Thus the phyllotaxis of the American larch is f , while that of the European larch is gV The phyl- lotaxis of the white pine and black spruce is -fa, while other pines with thicker cones exhibit in different species the fractions 5 8 T , f , and f j- ; and not only do the phyllotaxes differ, but also the primitive direction of the primary spirals. It is well known that the turpentines formed by different pines differ in a similar manner, as to their rotatory power upon plane polarized light ; and possibly these differences may be connected with differences in the phyllotaxis and spiral B. Opposite Leaves. The simplest case of opposite leaves is that of two leaves produced always at the same node, and at op- posite sides of the stem, the internode being in this case the interval between two successive pairs of leaves, instead of the in- terval between two successive leaves. "When the opposite leaves that grow at the same node are more than two, they are called a whorl, and the leaves are said to be whorled or verticillate. It is generally found, whether the leaves be simply opposite or whorled, that each successive set of leaves occupies the spaces on the stem intermediate between the leaves of the last set, so that the stem presents twice as many vertical ranks of leaves as there are single leaves in any whorl. In this case, the opposite or whorled leaves are said to be decussate; but it sometimes happens, though very rarely, that the entire whorl follows a spiral order in the growth of the stem, each leaf of the whorl obeying some law ofphyllo- 136 ELEMENTS OF NATURAL HISTORY. taxis, which is the same for all, and analogous to the spiral ar- rangement of alternate leaves already described. The leaf grows from the stem, like the young plant from the seed, at first by the aid of two auxiliary leaves called stipules, which are somewhat analogous to the cotyledons of the young stem, Fig. 69 (Quince). Sometimes these are altogether absent, and in many cases they fade away as the leaf expands, like the coty- ledons. Whenever stipules exist, they seem to be a provision for the growth of the young leaf which, like the young stem, requires a special organ for the digestion of its food in the earlier periods of its growth. The other parts of the leaf are the leaf stalk, or petiole, and the blade, or lamina : the petiole is sometimes wanting, in which case the leaf is sessile, or has its blade resting immediately on the stem that bears it, and sometimes also there is no proper blade, but the whole leaf is cylindrical, or stalk-like. The leaf, in general, is to be regarded as a contrivance for increasing the green surface of the plant, so as to expose to the light and air the largest amount possible of cellular tissue, or parenchyma, containing the green matter of vegetation, or chlorophyll, upon which the light exerts its peculiar action in digesting the juice of the crude sap. The leaves are, therefore, to be regarded as expansions of the cellular tissue of the middle, or green bark, developed into a thin flat layer, and stiffened throughout by woody fibres, or veins, which are connected both with the woody fibres of the liber, or inner bark, and with the outer zone of the woody layers of the stem. These veins, formed by bundles of woody fibre, are distributed through the blade of the leaf in two diffe- Fig. 69. VARIETIES OF LEAVES. '37 rent ways. They are either reticulated, as in Fig. 69, by succes- sive subdivisions, or they run parallel to each other, as in Fig. 70 (Eucharis), with only a few transverse veins connecting the main branches, and are then called nerved leaves. As a general rule, to which, how- ever, there are many exceptions, reticulated leaves are characteristic of exogens or dico- tyledons, while nerved leaves are characte- ristic of endogens or monocotyledons. The venation of the leaves is correlated with their general form and appearance, and names are given to leaves, of great impor- tance in descriptive botany, which can be best understood by referring each form of leaf to the mode of distribution of its veins, or primary bundles of woody fibres. Fig. 70. The principal varieties of leaves are the following : Fig. 71. (.) The Needle-shaped leaf (acicular\ Fig. 71 (Pinm exc This is well shown in Pines. '38 ELEMENTS OF NATURAL HISTORY. (b.} The Palmate leaf,~Fig. 70 (Norse chestnut} : both veins and leaf are said to be palmate, or like the fingers of the hand spread out. (c.) Serrate or Dentate Leaf, with pinnate nervation, Fig. 73 (Oak}. There are many varieties of this leaf. (d.} Pinnate Leaf. Fig. 74 (Acacia.} The preceding are some few of the many varieties of leaves of the reticulated type. Of the nerved leaves there are two principal kinds, one shown in Fig. 70 (Eucharis} in which the nerves run parallel to the midrib, and the other shown in Fig. 75 (Nile Lily], in which the nerves or veins, parallel to each other, form two series of lines, making ^>' angles at each side of the midrib ; both these sorts of nerved veins are commonly found in endogens, as in Grasses, the Banana, &c. The essential function of the leaf is to elaborate the sap conveyed to it from the rootlets, by the ducts and vessels of the woody stem; and to transmit back 74- Fig. 75. again into the stem, through the vessels of the liber, the digested, plastic sap, capable of depositing new cells and tissues. This function is exercised chiefly by evaporation, which in the case of many plants is effected upon a scale that is truly extraordinary. VARIE TIES OF LEA FES. 1 3 9 The Eev. Dr. Hales found that a Sunjloicer, three and a half feet high, with a surface estimated at 5616 square inches, perspired at the rate of twenty to thirty oz. av. in twenty-four hours, or seventeen times more than a man. This loss of water, hy evapo- ration, inspissates the juices of the leaf, and so causes, by endos- mose, the ascent of the sap. It also causes the deposition of mineral salts in the cells of the leaf itself, and especially of its petiole, and so gradually tends to the death of the leaf which is effected in exogens by a true mortification of the stalk, which drops off from the stem at the close of the autumn ; and in the case of the endogens the same effect is produced by causing the gradual death of the leaf from above downwards, leaving the de- cayed stalks adherent to the stem, and withering around it, in- stead of being amputated as in the "fall of the leaf" of exogens. " There is not wind enough to twirl The one red leaf, the last of its clan, That dances as often as dance it can, Hanging so light and hanging so high, On the topmost twig that looks up at the sky." Christabel. 10. The Flower. The organs of the plant already considered are all devoted more or less to the great function of nutrition, which is essential to the continued existence of the individual. We have now to consider the structure of the flower, which is the organ specially devoted to the function of reproduction, which is essential to the continuance of the species. Flowers grow from buds, similar in form and structure to the leaf buds from which the branches are produced ; and such buds as produce flowers are regarded by botanists merely as leaf buds, specially modified in order to fulfil certain functions. Leaf buds, as we have seen, are either terminal or axillary ; and in like manner the flower buds are either terminal or axillary; giving origin to two distinct kinds of inflorescence, readily distinguishable from each other. These kinds of flowering are called determinate and indeterminate. 14 ELEMENTS OF NATURAL HISTORY. A. Indeterminate inflorescence. In this case all the flowers are produced in the axils of the leaves of the growing branch, and the inflorescence is called indeterminate, because the flowers produced are indefinite in their number, which depends merely on the vigour with which the branch continues to grow, and to pro- duce flowers from the axils of its leaves. This form of inflorescence is represented in Fig. 7 6, .which shows the whole flowering branch supported on a common peduncle, while each flower is supported on a pedicel or partial peduncle. When the flowers are stalked, as in the figure, the whole flowering pe- duncle is called the axis of inflorescence, and when the flowers are sessile it is called a rhachis (/3a%is). Sometimes the flowers are produced on a flattened surface, instead of on a growing axis, and in this case the flattened surface is called the receptacle. The leaf bud producing its branch and leaves, imitated the seedling in having stipules to repre- sent the cotyledons ; in like manner, the flower bud is frequently aided in its earlier growth by the nourishment supplied to it by one or more leaves developed upon the partial peduncles, which are called bractlets. The term Bract is applied to the more or less modified leaf subtending the partial peduncle. The following varieties of indeterminate in- florescence are universally recognized by botanists (.) Raceme (racemus), (Fig. 76). In this case, each flower, mounted on its own footstalk, is deve- loped in its proper order of phyllotaxis, on the axis of inflorescence. The Lily of the Valley, and Currant, are good examples of the raceme. The raceme generally possesses both bracts and bractlets, but the latter are often so small as to escape notice. The lowest blossoms, Fig. 76. being first developed, are the oldest, and the youngest bios- ARRANGEMENT OF FLOWERS. 141 soms occur nearest the tip of the axis; regarding, therefore, the extremity of the axis as a centre, the inflorescence is often said to be centripetal, and this character belongs universally to the indeterminate inflo- rescence caused by axillary flower buds. (b.) The Corymb (jcd/w^ov), (Fig. 77) This is the same as a raceme, in which the central axis is shortened and the lower pedicels lengthened, so as to Fig. 77. bring all the flowers nearly to the same level ; in the case of the corymb the term centripetal applied to the flowering becomes very appropriate : if we suppose the axis of the Corymb to be still fur- ther reduced in length, as often happens the growth from leaf buds, we shall obtain 0.) The Umbel (umbella), Fig. 78. This is a flower cluster, in which all the pedicels seem to spring from the same point, or top of the peduncle, so as to form a series of branching rays, resembling the ribs of an umbrella. These branching pedicels are called rays, and the united bracts are called an involucre. The Corymb may be well studied in the Candytuft, and the Umbel in the Primrose. The centripetal character of indeter- minate inflorescence may be well seen in the Umbel and Corymb. In the preceding cases of inflores- cence the flowers were all stalked; in the fol- lowing they are sessile. (d.} The Spike (spica), Fig. 79, is a flower cluster, with a lengthened axis, and sessile flowers ; and is a raceme without pedicels to its flowers. It is illus- trated by the Mullein, Plaintain, and Verbena. 142 ELEMENTS OF NATURAL HISTORY. ( 377- 2 vii. August ii to September 7 (27 days), 230.9 ,, . . The total quantity of water given off by the wheat in the 172 days was 113527 grains, and by the peas, 109082 grains ; and the mineral derived from the wheat was 36.49 grains, and from the peas 43.16 grains; showing that the ivheat absorbed 32.14 grains of mineral salts, and thepeas 39.59 grains for every 100000 grains evaporated by their leaves. The force of Endosmose is fully sufficient to account for the ab- sorbing power of the rootlets of plants, and for the ascent of their sap ; and it also serves to account for the selecting power now generally attributed to the rootlets; for the endosmotic force varies, not only with the density of the two fluids separated by PLANT CIRCULATION. 163 an organic membrane, but with the nature of the fluids themselves and of the membrane. Thus, the careful experiments of physi- cians have proved that the relative motions of fluids, under the influence of endosmose, depends upon their specific heat ; so that the fluid possessed of the greatest coefficient of specific heat always moves towards the fluid possessed of a lesser coefficient; from this it follows that pure water (which has the greatest specific heat of all fluids) must move towards any other fluid ; and in the endos- motic action, solutions of salts, having a high specific heat, will readily pass through the membrane, while those possessing a low specific heat will be left behind. The natural food of plants consists chiefly of water, carbonic acid, and ammonia together with small quantities of mineral alts, varying with the kind of plant. The natural excretions of the animal kingdom consist of water, carbonic acid, and urea, which is rapidly converted into carbonate of ammonia together with some mineral salts, in general similar to those used in the food of plants, such as phos- phates and other salts of magnesia, soda, potash, &c. These two kingdoms of nature thus compensate each other's action, the excretions of one forming the food of the other, and vice versa. The carbonic acid excreted by the lungs of animals, and produced by the combustion of coal and wood, becomes a constituent part of the air we breathe, and would destroy animal life if it attained to four per cent, of that air ; but, by the won- derful compensation of the vegetable kingdom, it is absorbed by the leaves of plants in respiration, and resolved into carbon and oxygen ; the former of which becomes fixed in the woody fibres of the plant, while the oxygen is given back to the atmosphere, and renders it again fit for the respiration of animals. The urea excreted by the kidneys of animals is rapidly con- verted into carbonic acid and ammonia, both of which are dis- solved by moisture, and conveyed to the roots of plants, whence they are pumped up by endosmotic force into the, leaves. M 2 164. ELEMENTS OF NATURAL HISTORY. The food of plants may therefore be thus classified, according to its composition and mode of reception : f Ammonia, ) , i. Nitrogenous food, < ., > by endosmose. f "Water, . . by endosmose. ii. Non-Nitrogenous food, < Carbonic Acid, by respiration, v. partly by endosmose. in. Mineral Salts, f Phosphates,^) Chlorides, Bromides, Iodides, Fluorides, Silicides, J by endosmose. The sap brought from the roots, in its passage up the stem, is variously modified by dissolving other substances in the cells it passes through, and ultimately reaches the leaves, where it under- goes still greater changes, by being brought under the influence of the function of respiration, which must be now described. 2. Respiration of Plants. The respiration of plants is the inverse of the process called the respiration of animals. It is well known that animals of the higher orders inspire and expire air by means of their lungs, which are the organs proper to respiration; the inspiration and expiration depending on the move- ments of the intercostal muscles, which connect the ribs that en- close the cavity of the chest containing the lungs. In animals, the inspired air is deprived of a portion of its oxygen, which is replaced by carbonic acid in the expired air ; but in plants, the process of respiration, although not performed by alternate inspi- rations and expirations, is the inverse of the preceding, and con- sists in the absorption of carbonic acid by the leaves, and its re- placement by the exhalation of oxygen through the stomates of the same organs. Atmospheric air is composed of seventy-nine parts of nitrogen to twenty-one of oxygen, with a minute quantity of carbonic acid ; and it is the latter gas that furnishes the proper PLA XT RESPIKA TION. 1 65 source of the special respiration of plants. This fact is established by the following observations : 1 . If a plant be allowed to grow in a glass bell filled with air that is permitted to remain unchanged for a certain time, and this air be analyzed from time to time ; it will be found to have lost carbonic acid and to have gained oxygen. 2. A plant produced from a seed may be allowed to vegetate in pure sand watered with distilled water, so as to preclude the possibility of any food, other than water, reaching it except by respiration from the air. If, after a certain period of growth, the plant be analyzed, and compared with the analysis of other seeds similar to that which produced it, the result of the ana- lysis is always found to be, that the plant gains carbon, which must have been derived directly from the air, which contains this substance only in the form of carbonic acid ; and hence we infer, as in the former case, that growing plants have the property of decomposing carbonic acid by their leaves, and of giving back to the atmosphere the oxygen disengaged by the process of decomposing the carbonic acid. It has been repeatedly proved that the decomposition of carbonic acid, which is called the respiration of the plant, is effected by the agency of the green cells, containing chlorophyll, and that sunlight is necessary to the perfection of this function. "When plants are excluded from the influence of the sun's light, their green parts become blanched, and they cease to respire ; that is, they cease to convert the carbonic acid of the air into carbon and oxygen ; so that the respiration of plants is not a function, like that of respiration in animals, necessary to their existence ; but is a function whose activity requires a special stimulus, like that of sunlight, for its manifestation. When an animal ceases to breathe, it dies ; and in the highest animals, such as man, a cessation of breathing for sixty-five seconds is sufficient to cause death ; in plants, however, the cessation of respiration causes a change 1 66 ELEMENTS OF NATURAL HISTORY. of colour only, but not a cessation of growth, much less of life itself. Under such circumstances, however, plants suffer much, although not so much as animals ; they never acquire proper developement, no green colour appears in their stems or leaves, little or no woody fibres are formed in their tissues, and their whole energy is expended in the produc- tion of weak watery shoots ; and, finally, they cannot con- tinue to live under such circumstances, unless supplied with organic nutriment ; for they have been deprived of the sun- light, and sun-heat, which are the natural forces that enable the plant to convert mineral into organic products. This remarkable process, called the respiration of plants, might more justly be described as a. deoxy dating process, which the green leaves and cells of plants are capable of effecting under the sti- mulus of sunlight. It bears no analogy whatever to the respi- ration of animals, which consists simply of the excretion of car- bonic acid, produced by the oxydation or combustion of the animal tissues, and which is accompanied, as everybody knows, with the liberation of heat, that measures exactly the force consumed in the combustion. In the respiration, or rather deoxydation, ef- fected by plants under the influence of sunlight, on the contrary, we have exhibited the reverse process of the storing up, instead of the expenditure of force, by the action of vital agencies, and this action is accompanied by the production of cold, instead of heat, and also by the conversion of lower forms of chemical compounds into higher forms. The following list of non- nitrogenous vegetable products shows how intimately they are related to carbon and water, although it is not to be supposed that they are simply formed of these sub- stances : + loj atoms of water. + 10 +10 ,, +14 >, -f- n i. Cellulose, . 12 atoms of carbon 2. Starch, . . . 12 3. Dextrine, . . 12 4. Grape Sugar, . 12 5. Cane Sugar, . 12 ,, SECRETION OF CARBON. 167 Chemists are not agreed as to the mode in which carbon be- comes fixed by plants ; but the views of Draper are more gene- rally received than other theories on this subject. Mr. Draper considers that the nitrogenous elements brought up from the roots into the leaves perform the part of a ferment, and excite what is called contact action upon the carbonic acid introduced through the stomates of the leaves, and so produce the fixation of carbon, and the liberation of oxygen from the green cells ; and even though we cannot understand the precise mode of operation, we can readily conceive the extreme importance of this remarkable process, which ought to be called a secretion of carbon, rather than a respiration of the plant. 3. Nutrition of Plants. The chief food of plants, as already stated, consists of ammonia, carbonic acid, and water of which the ammonia and water are supplied principally by the roots, and the carbonic acid by the atmosphere, to the leaves. The absorp- tion of carbonic acid and its deoxydation by the green cells are effected only under the influence of sunlight ; while, during the night, and always when the plant is grown in total darkness, an inverse process goes on, analogous to that which maintains the life of animals, and which consists chiefly of the oxydation of carbon into carbonic acid by the absorption of oxygen from the air. In fact, when a plant is grown under a bell glass, and is found to give out oxygen, and absorb carbonic acid, this result is really not a simple action of the plant, but is the difference of two distinct and opposite actions one of respiration (so called), by which carbonic acid is absorbed and oxygen set free ; and the other, of digestion or nutrition, by which oxygen is absorbed and carbonic acid set free. This process of nutrition seems to be constant, and to be necessary to the continued life of the plant, as it is well known to be to the continued life of the animal ; while the process of respiration varies with the degree of exposure of the plant to sunlight, and is a function, like that of muscular exercise in the animal, necessary rather to the health of the being 1 68 ELEMENTS OF NATURAL HISTORY. than to its bare existence. Very little is as yet known of the inner chemistry of this function of nutrition, and still less of its relations to the more active function of respiration. Judging by the excess of the products of respiration in healthy plants, over the products of the excretions produced by nutrition, we are entitled to say, that the plant gains, instead of losing force, during the whole period of its existence, and terminates a useful career, like a miser, by storing up organic products, which after- wards serve for the nutrition of various forms of animal life, such as the Herbivores, which in their turn store up nitrogenous food for the nourishment of still higher forms of existence, such as dogs and men. " Happy," says a French proverb, " are the children of the damned," for they enjoy without scruple the sav- ings of avarice and crime. The innocent plants produce and yield up their stores to others without any drawback. The excretions and secretions formed by plants are the joint product of all the chemical reactions caused both by respiration and digestion ; and some of the most important of them have been already mentioned. Their composition, in atoms, is as follows : c. H. o. i. Starch, ..... 12 . 10 . 10 ii. Dextrine, . . . . 12 . 10 . jo in. Cellulose, .... 12 . ioj . ioi v. Cane Sugar, . . . 12 . 1 1 1 1 1 1 vi. Fruit Sugar, . . 12 12 . 12 vn. Starch Sugar, . . 12 . '4 14 vni. Mannite, . . . 12 . '4 12 ix. Oxalic Acid, . . 2 o . 3 x. Malic Acid, . 8 . 4 8 xi. Citric Acid, 12 . 5 1 1 xn. Tartaric Acid, . . . 8 . 4 10 xni. Tannic Acid, . . . 18 . 5 9 The volatile oils excreted by plants are very numerous, and are usually secreted in glands, either external or internal, situ- PLANT NU1RITION. 169 ated in the herbaceous parts of plants. They are seldom pure, but contain dissolved resinous matters, camphor, and active principles of various kinds. Resinous and waxy secretions are very varied, both as to mode of occurrence and composition ; they are found on the sur- face of the leaves and fruits, and on the outer coat of the pollen of many plants. The milky juices of plants (latex) contain essential oils, gum resins, starch grains, and alkaloids, suspended in water, and forming a kind of emulsion. These juices are found especially in certain natural orders of plants, and are frequently of great commercial importance as, for example, opium, caoutchouc, and gutta percha. The alkaloids form an important group of vegetable products, many of which are poisonous, and which agree with each other in containing nitrogen. They are much used in medicine, espe- cially of late years, and are highly esteemed ; among the most important may be mentioned c. H. N. o. i. Conia, 10 . 15 . i . o n. Nicotina, . . . . 10 . 7.1. o in. Cinchona, .... 40 . 24 . 2 . 2 iv. Quinia, . . . . 40 . 30 . 2 . 10 v. Morphia, . . . . 34 . 19 . i . 6 vi. Narcotina, . . . 46 . 25 . i . 14 vn. Strychnia, .... 42 . 22 . 2 . 4 vin. Brucia, .... 46 . 26 . 2 . 8 ix. Caffeina, ....16.10.4. 4 Conia is the alkaloid that gives to Hemlock (Conium macula- turn) its celebrated poisonous properties ; it pervades the whole plant, but is most easily obtained from the seeds. Nicotina agrees with Conia in being destitute of oxygen ; it forms the poisonous principle of tobacco (Nicotiana tabacum), and occurs in that plant in combination with malic and citric acids. 170 ELEMENTS OF NATURAL HISTORY. Cinchona and Quinia are valuable alkaloids, found in the several varieties of pale, yellow, and red Peruvian larks. These valuable remedies for ague were first made known by th,e Jesuit missionaries in South America, and active exertions are now being made to naturalize the cinchona plants in Hindostan. Morphia and Narcotina are two of the alkaloids occurring in the Poppy, and forming essential parts of crude opium ; Morphia constitutes the chief active ingredient in this drug, and is a well known powerful narcotic poison ; Narcotina forms an ingredient of opium almost as important as Morphia, and, like this alkaloid, is a powerful narcotic poison, only less active. Strychnia and Brucia are alkaloids occurring in the St. Ig- natius bean (Strychnos nux vomica), and both act as powerful poisons, producing symptoms the opposite of those caused by Nicotina, but equally fatal. These poisons have been successfully used as antidotes (physiological) to each other. Caffeine, or Theine, is the alkaloid present in the tea and coffee plants, and in other plants similar to them in properties, such as the Mate or Paraguay tea plant. This valuable alkaloid forms a portion of the daily food of three- fourths of the human race, and exerts important physiological effects of a most beneficial kind, which cannot be here further considered. Like most stimulants, when used in excess, it produces loss of sleep, ner- vous excitement, and symptoms of congestion of the brain. From the foregoing statement it will be seen that the secre- tions formed by plants, under the joint influence of the absorption of nitrogenous food by the roots, and of carbonic acid by the leaves, are very varied, and but little known. They consist of nitroge- nous and non- nitrogenous products, which have been studied by the chemists, but whose secretion and distribution in the plant that forms them are almost wholly unknown to the bota- nist. 4. Reproduction of Plants. Plants are reproduced.either by subdivision, natural or artificial, or by the formation of seeds, PLA NT REPROD UCTIOX. 1 7 1 which reproduce the image of the original plant in its integrity. The first kind of reproduction of plants is sometimes called vege- tative multiplication, in order to distinguish it from true repro- duction, and is not without numerous analogies in the animal kingdom also. A. Vegetative Multiplication. One of the most remarkable examples of vegetative multiplication is to be found in the history of the Weeping willow (Salix Salylonica), which is a native of Mesopotamia, and immortalized in the most beautiful of all the Hebrew Psalms, cxxxvii. By the rivers of Babylon we sat down ; And wept, when we remembered thee, Zion. We hanged up our harps On the "Willow trees of the streams. They that made us captives asked for a song ; Our spoilers asked us for mirth. Sing to us, Oh sing to us, the songs of Zion ; How shall we sing ; how shall we sing ! The song of Jehovah in the land of the stranger ? In the reign of Queen Anne, the poet Pope was staying with the Countess of Suffolk, when she received a parcel from Spain, bound with withes, which seemed yet alive ; Pope took one of them and planted it in his garden at Twickenham, where it be- came celebrated as Pope's Willow. It was originally introduced by the botanist Tournefort into Europe, and since its introduc- tion it has been propagated by cuttings only and not by seeds, so that every weeping willow in Europe is literally part of the same tree, that possibly still grows on the banks of the Euphrates. The foregoing is a remarkable occasional instance of vegetative multi- plication in the case of one of the higher plants ; but in the lower forms of plants this is the mode of reproduction that usually occurs, and by which the plant is propagated. I 72 ELEMENTS OF NATURAL HISTORY. In the group of plants called Thallophytes, where the entire organization consists of cells, and there is no leaf structure of any kind, the buds (gemmce) are congeries of cells, formed by division of original cells, and ultimately separated from the parent plant by a process of spontaneous fission, similar to that observed in the lower forms of animal life, such as sponges and polyps. This pro- cess of multiplication in the Thallophytes is strictly analogous to the vegetative multiplication of the higher plants by means of buds ; but it is remarkable that in many Thallophytes, perhaps in all, there is a periodical formation of true reproductive cells, male and female, analogous to flowering, the union of which produces cells capable of commencing a new growth, and of reproducing the original plant in a manner strictly analogous to the formation of seeds, by the fertilization of the ovules by the pollen. In the flowering plants, the principle of vegetative multipli- cation is exemplified in the leaf buds already described, which are capable, either naturally or by artificial means, of being de- veloped into new plants, of the same kind as that which produced them. Thus the bulbiferous Lily is multiplied by means of axil- lary leaf buds that are spontaneously detached from the parent plant, and similar productive buds are often produced, instead of flowers, by the several species of Garlic, in which such buds are called cloves, and are highly prized, on account of the concentrated oils which they usually contain. In the Potato, the tuber is formed from the branch of the stem, and produces buds called " eyes," which are separable from the parent stem, and capable of producing each a new plant. A similar condition prevails in the Jerusalem Artichoke, Dahlia, and other well known cultivated plants. The leafy shoots, called runners in the Strawberry, and called offsets in the Houseleelc, are simply modifications of ax- illary buds, and are examples of the mode in which the ve- getative multiplication of plants is variously effected, by a principle that seems to pervade the whole vegetable kingdom, PLANT REPRODUCTION. from its lowest members to the highest, and which passes beyond that kingdom, into the lower regions of the animal kingdom. Gardeners take advantage of this principle in the several opera- tions described as forming slips, cuttings, layers ; and also in budding and grafting ; all of which consist in detaching either buds, or shoots proceeding from buds, from the parent plant, and causing them to grow, either directly in the ground, or in the cambium layer of some other plant. B. True Reproduction, It was at one time thought by bota- nists that the two great subdivisions of the Vegetable Kingdom ; viz., phanerogams and cryptogams, might be distinguished from each other as being propagated, one by a true reproduction, and the other by vegetative multiplication ; but it is now generally recognized that both classes of plants are actually reproduced by both processes. (a.) Flowering plants. The production of seeds depends on the fertilization of the ovule by the pollen ; the ovule is produced by the pistil, and the pollen is produced by the stamen ; when both are fully ripe, the pollen is scattered by the wind, or carried accidentally by an insect, and reaches the stigma of the pistil, which is destitute of epidermis ; the pol- len, as it were, takes root in the stigma, and a long slender filament grows down from it, until it reaches the ovule, Fig. 108, which at once begins to grow, and en-' larges until it becomes the seed, provided with its radicle, its plumule, and cotyledons, already described; and at the same time the surrounding structures partaking of the general stimulation and growth, form around the seeds the various kinds of fruits mentioned before, as drupes, achenes, &c. Fig. 108. 174 ELEMENTS OF NATURAL HISTORY. (b.) Flowerless Plants. There are various modes of true repro- duction, as distinguished from vegetative multiplication, recognized in the flowerless plants, or cryptogams, all, how- ever, reducible to the following: In the higher cryptogams the female organs are termed archegonia, the male antheridia. Within the latter are formed peculiar ciliated bodies, the antherozoids, which, entering the neck of the archegonium, reach its central cell, and thus the act of fertilization is effected. In the lower cryptogams the female organs essentially corre- spond to the contents of the archegonia among the higher. Their fecundation is, in like manner, effected by contact with anthe- rozoids. Such a mode of reproduction has been observed in several Algae. The true reproduction of the Lichens and Fungi is still very imperfectly understood. Some of the lower Algae are reproduced by a simple process termed conjugation, or the union of two slightly dissimilar cells, supposed to represent the germ-cells and sperm-cells of higher plants. Flowerless plants are also propagated by means of spores (air6poy the additional possession of a nervous system, which is capable of receiving sensations, and of issuing volitions that produce move- ments in special organs adapted to this use. In the Vegetable Kingdom all the organs and life were so far similar that the description of one plant might almost be said to have served us for a general description of all plants, so that the classification of plants became subordinate to the descrip- tion of organs and of their uses. In the Animal Kingdom, on the other hand, the modes of receiving sensations and of issuing volitions from the nervous system are so various, that the Clas- sification of Animals becomes of primary importance. CLASSIF1CA TION OF ANIMALS. 1 8 5 i. Classification. It is, therefore, necessary to commence the description of the Animal Kingdom with a brief sketch of the classification of animals, founded on the general structure of their nervous system. In all animals the faculties of sensation and volition reside in a peculiar kind of substance, called nerve, which is capable of receiving sensations and issuing volitions ; and is concentrated variously into centres, called ganglions or cords, according to their shapes ; the varieties of which constitute the most natural foundation for our classification. In the highest animals, the great mass of nerve substance is arranged in a long spinal cord enclosed in a series of bones, articulated with each other, each of which is called a vertebra ; and the upper or anterior end of this mass of nerve substance is expanded into a bulbous portion, called the brain ; in which the faculty of thinking resides, in ad- dition to the faculties of sensation and volition possessed by it, in common with the spinal cord. Aristotle was the first writer that observed this important principle of classification of animals ; and he noticed, also, that animals that possessed a spinal cord enclosed in vertebrae had also red blood, while the animals that did not possess a spinal column had white blood, destitute of the colouring matter that characterizes the blood, or circulating fluid of the higher animals. From the time of Aristotle, therefore, animals have been di- vided into two groups, named by Lamarck and Cuvier, Vertebrate and Invertebrate; of which the former have been most studied by the earlier naturalists, and the latter by modern natura- lists. In the Vertebrate animals the nervous system consists of two distinct parts ; one of which presides over animal life, and is the instrument of thought, sensation, and volition ; while the other presides over organic life, and regulates the functions of nutrition, circulation, respiration, and reproduction. 1 86 ELEMENTS OF NATURAL HISTORY. The first group of nerves is called the cerebro-spinal system, and consists of the brain and spinal cord forming a continuous body, and enclosed in the brain-case or skull, and in the series of bony rings called vertebra. To this part of the nervous system belong the reception of sensations, the issuing of volitions, and the power of thought. This group of nerves is called the Nerve System of the Animal Life. The second nerve system of Vertebrate animals is called the Nerve System of Organic or Vegetative Life ; and is also known by the names Sympathetic or Ganglionic System. It is divisible into two parts placed in front of the spine; one composed of several ganglions (called semilunar and cardiac], whose branches are distributed to the primary organs of digestion and circulation > and the other consisting of two knotted cords, extended along the whole length of the spine, and communicating freely by branches with the ganglionic plexus, and with the cerebro-spinal nerves. These two subdivisions of the sympathetic nerves are found in verte- brate animals, and are met with separately in the lower (invertebrate) forms of life. For example, in the Mol- lusks, the nervous system consists (Fig. 109) of a number of distinct gangli- onic centres, joined by con- necting filaments of nerve, as in the ganglionic plexus of man ; and in the Articu- Fig. 109. lates, the nervous system ** ' 10 - (Fig. no) assumes the form of a double row of knotted nerves, each knot corresponding to a separate joint of the body. NERVE-CENTRES. 187 Neither, however, of these systems is identical with the cere- bro- spinal system of the Vertebrates. The organs of the senses are developed in the Vertebrate animals to a degree proportionate to the developement of the cerebro-spinal system. The organs of four of the senses sight, hearing, smell, and taste are situated in the anterior part of the head, included in bony cavities. The sense of touch is in some animals especially developed in the fingers, in others in the lips, and in others probably in the tongue. The sixth or muscular sense, to which we owe our idea of force, and sensation of fatigue, is doubtless present in all animals en- dowed with muscles and capable of locomotion. It is an especial characteristic of Vertebrate animals, that they possess an internal skeleton, of which the vertebral column forms the stem, and to the several parts of which the muscles are attached. The vertebral column and skull, with their en- closed cerebro-spinal cord of nerve substance, are the only essential parts of the internal skeleton, for the four limbs are wanting in most snakes and in some fishes, and the ribs are wanting in the frogs and others. The body of Vertebrate animals is gene- rally symmetrical on the two sides, right and left ; and the organs of animal life, the nerves and muscles, are symmetrically placed.* There are never more than four limbs ; some have only * The organs of the organic life are not always symmetrically placed in Vertebrate animals. Thus the heart is on the left side and the liver on the right, notwithstanding the high authority of Moliere to the contrary. GERONTE. " II n'y a qu'une seule chose qui m' a choquee ; c'est 1'en- droit du foie et du coeur. II me semhle que vous les placez autrement qu'ils ne sont ; que le coeur est du cote gauche, etle foi du cote" droit." SGANARELLE. " Oui, cela etait autrefois ainsi ; niais nous avons change tout cela, et nous faisons maintenant la medicine d'une methode toute nou- velle." Le Medecin Malgre lui. c - 1 88 ELEMENTS OF NATURAL HISTORY. one pair, and both are occasionally absent. The blood of verte- brates is red, and the sexes are distinct. They have, mostly, two jaws, one situated above the other, the lower jaw having most motion; and the movement of the jaws ^ v is vertical, and not lateral, as is the case in articulate animals. The jaws are usually furnished with teeth, which in some cases, as in birds, are wanting, or replaced by horny plates. The intestinal tube, in vertebrate animals, receives the secre- tions of many glands, of which the most important are, the sali- vary glands, the pancreas, and the liver. The masticated food, altered by the action of these secretions, and of the gastric acid of the stomach, is absorbed by delicate vessels, called lacteals, from the mucous surface of the intestines, and is carried by these vessels to the veins (especially the left subclaviari), where it enters the general circulation of the blood, and restores to this fluid the elements it has lost by the wear and tear of daily work. Other vessels, of capillary size, and called lymphatics, absorb from all parts of the body a watery lymph, composed of excretions from the capillary blood vessels ; and the whole lymphatic and lacteal system, of which the spleen probably forms a part, constitutes a complex system of nutrition and excretion, the details of which are but little known. The veins having received the contents of the lacteal and lymphatic vessels, carry the blood to the heart, from which it is driven into the respiratory organs, where it is oxydated by the direct action of the air in lungs, or by the air contained in water passing through gills. In either case, the heart of Vertebrates receives unoxydised blood, and forwards it to respiratory organs, where it becomes oxydised. When the oxydised blood returns again to the heart, it is circulated by means of the arteries into all the organs of the body, which are thus fed continually by the blood, constantly replenished, through the stomach and intestines, with food, and through the respiratory organs with oxygen. The ultimate products of all the chemical changes that take NUTRITION AND EXCRETION. 1 89 place ill the blood during the complex processes of nutrition and respiration, are 1. Water. 2. Carbonic Acid. 3 TJrea. Water finds its natural outlet through the skin and lungs, as vapour ; and through the kidneys, as water. Carbonic Acid finds its natural and healthy outlet through the lungs or gills, where it is exchanged for an equivalent amount of oxygen absorbed. Urea, which is an excretion peculiar to the Animal Kingdom, is invariably discharged through the kidneys, which are organs especially devoted to this purpose. Urea has the following com- position : Two atoms of Carbon, .... 1 2 ... 20 per cent. Four atoms of Hydrogen, ... 4 ... 6 Two atoms of Nitrogen, ... 28 ... 47 ,, Two atoms of Oxygen, .... 16 ... 27 60 100 Animals differ from vegetables, chemically, in the larger per- centage of nitrogen that enters into their composition ; and it is a remarkable fact that this nitrogen always leaves the animal system under the form of urea, a substance that becomes rapidly transformed into carbonate of ammonia, which is readily absorbed, in turn, by plants, and so completes the cycle of chemical changes, by means of which the Animal and Vegetable Kingdoms are mu- tually dependent upon each other. The organs especially appropriated to the excretion of urea in the Vertebrate animals are the kidneys, which are present in all animals of this class. The kidneys consist, in their internal structure, of fine tubules, which in the lower Vertebrates unite to form branches that open into excretory ducts (oty>//T7y/>es) run- ning along the whole kidney ; in birds and mammals, the tubules 190 ELEMENTS OF NATURAL HISTORY. unite to form pyramidal bundles, which are arranged round the cup-like commencements of the ureters; and the two ureters, again, converging from the symmetrically-placed kidneys, enter the urinary bladder, or sack, in which the secreted fluid is col- lected before being discharged from the body. The Vertebrate animals are divided into four classes, originally proposed by LinnaBus. This classification is natural, and based upon the temperature of the blood and internal organs ; upon the various forms of the heart ; upon the differences in the respira- tory organs, which are either lungs or gills ; and on differences in parturition, such as the laying of eggs, or bringing forth of living young. The four classes are : 1. Mammals. 2. Birds. 3. Reptiles. 4. Fishes. Mammals and Birds have warm blood, and so are distinguished from Reptiles and Fishes ; they are distinguished from each other by the Mammals being viviparous, and the Birds being ovipa- rous. Reptiles and Fishes have cold blood ; and are distinguished from each other by the Reptiles having lungs, and the Fishes having gills. 2. Mammals. The Mammals are the highest form of animal life, and include Man himself; they are vertebrate warm-blooded animals, breathing by means of lungs ; and they differ from Birds in having a muscular midriff or diaphragm, separating the cavity of the chest from that of the belly ; or dividing the internal organs of circulation and respiration from those of digestion and reproduction. Mammals differ also from birds in having glands (mamma") which secrete the milk, with which the mother feeds her young ; and in being viviparous, instead of oviparous. SKELETON OF MAMMALS. 19 1 A. Skeleton. The skeleton of mammals consists essentially of a series of bones, articulated with each other, called vertebrae, which enclose the brain and spinal cord; together with four limbs, or locomotive organs, which undergo great modifications, according to the uses to which they are destined to be applied. Fig. in. Figs. 1 1 1 and 112, representing the skeletons of the Camel and Fig. 112. of the Seal, serve to show the plan on which the whole skeleton 192 ELEMENTS OF NATURAL HISTORY. is constructed, and also the modifications undergone by the limbs, according to the requirements of the locomotion proper to the element in which the animal lives. The skull, composed of numerous bones, encloses the brain, and is followed by the cervical vertebras composing the neck ; with one or two exceptions,* the vertebrae of the neck are always* seven in number, the number of bones being the same, for example, in the Giraffe and in the Whale. The dorsal vertebrae, corresponding in number with the ribs, which enclose the chest containing the organs of respiration and circulation, are generally thirteen in number : and it is very rarely that less than twelve or more than fifteen back bones occur, f The lumbar and sacral bones are more variable in number, the lumbar being generally six or seven, and the sacral bones ranging from one to nine, being generally four in number. The caudal vertebras, or tail bones, range from four to forty- six, and are more subject to variation than any other portion of the skeleton, except the limbs ; of which indeed the tail may be regarded as one. "Wherever it be situated, a vertebra consists essentially of a body or centrum, on the back of which the spinal cord lies, and generally in front of it the main artery of the trunk; the spinal cord is protected behind and laterally by bones amalga- mated with the body of the vertebra, and called spinous and transverse processes ; sometimes also, in the lower vertebrates, the main artery also is protected by bony processes, called chevron bones, or inferior spinous processes. These parts of a typical vertebra are shown in Fig. 113, which represents the pelvis and some of the tail bones of the * The three-toed Sloth has nine neck bones ; and the southern Manatee has only six. t One of the Armadilloes has only ten, the Pachyderms have from eighteen to twenty-one, and the Sloths have twenty-four back bones. VERTEBRAL COLUMN. 193 alligator ; the bodies of the vertebrae are marked b, the spinous processes sp, the transverse processes tr, and the chevron bones ch. These various parts of the vertebra serve not only for the protection of the spinal cord and abdominal aorta, but also form the origins and insertions of muscles, that move the head, the tail, and other parts of the vertebral axis. Their developement, therefore, varies greatly in different animals and in the different parts of the back bone of the same animal. The ribs are appendages of the dorsal vertebrae, and enclose the cavity of the chest ; they are usually articulated with the bodies of two successive vertebrae, and with the transverse pro- cess of the posterior of the two vertebrae. Anteriorly, the ribs are united by cartilages with the breast bone, or sternum. The posterior and anterior pairs of limbs are evidently con- structed on the same model, and attached to the trunk in the same way. The best type of the hind limb, or leg, may be found in the order of Reptiles. It is articulated to the body at the Fig. in- cavity of the pelvis, called the acetdbulum (). The pelvis is, in the Alligator, composed of four distinct bones, named Ilium, il. Isehium, isch. Marsupial, m. Pubes, p. and is shown in Fig. 113. o 194. ELEMENTS OF NATURAL BISTORT. The head of the thigh bone, or femur, plays in the socket, formed by the ilium and pubes. The thigh bone is succeeded at the knee-joint by the leg bones, tibia scad, fibula, and these again are followed at the ankle by the tarsal, metatarsal, and toe bones. The best type of the anterior limb is to be found in Birds, in which the office of the wing is predominant. The arm bone, or humerus, of the bird plays in a socket, formed of four bones that correspond to the four bones of the pelvis of the reptile, viz. : Acromwn, ilium. Scapula, ischium. Clavicle, marsupial. Coracoid, pubes. It is, fortunately for the learner, not necessary to know all .the details of the relation of the fore limbs to the hind limbs in mammals ; and it is sufficient to observe their general analogy. The arm bone is followed, at the elbow-joint, by the two bones of the forearm, radius and ulna ; and these again, like the bones of the leg, are succeeded at the wrist by the carpal, metacarpal, and finger bones. Of the four bones that, typically, form the pelvic or scapular arch, one or more may be absent, according to the uses to which the limbs of the animal are destined to be applied ; but it is im- portant to bear in mind, that the plan on which the mammals are constructed is simple and symmetrical with respect to their anterior and posterior limbs, or locomotive organs. The anterior limbs in the highest animals, as in man, cease to be used as locomotive organs, and are devoted to serve the brain, by a process described by Prof. Dana, as cephalisation of the fore limbs ; and he considers that animals ought to be classed in order of dignity, in proportion as their fore limbs are appro- priated, as organs of prehension, instead of organs of locomotion. The anterior limbs are never absent in mammals, but they are frequently destitute of a clavicle, and the acromion is often re- duced to be a mere process of the scapula. The coracoid, which iu birds and reptiles acts the part of a second clavicle, is found THE PELVIC AND SCAPULAR ARCHES. 195 as a distinct part of the scapular arch, in the Monotremes only among mammals. The arm bone and thigh bone resemble each other, and also the double bones of the forearm and leg, which admit of a rotation, more or less perfect in different animals, being accomplished. The bones of the wrist and ankle, and of the hand and foot, fingers and toes, are subject to many variations, which are of the highest value in classification. The fingers vary in number from one to five ; in the Horse they are reduced to one, which is regarded as the middle finger ; in the Ox, two fingers, index and middle, are constantly pre- sent, with rudiments of two other imperfect fingers. The toes undergo similar modifications, and do not always cor- respond with the fingers ; thus the Leopard has five fingers and only four toes ; the Hyaena has four fingers and four toes. B. Nervous System. The nervous system of mammals con- sists, as already described, of two parts a. Cerebro-spinal system. b. Sympathetic system. (). Cerebro-spinal System. The brain and spinal cord of man and the higher animals, Fig. 1 14, form a central mass of nerve substance, from which the nerves of volition branch out in all directions to the muscles, and towards which the nerves of sensation converge from all parts of the body. These nerves have been very ridiculously compared by po- pular writers to telegraph wires, and the brain to a galvanic battery that works the wires. The influence that travels along the nerves bears no resemblance whatever to an electric cur- rent, for it moves only at the rate of 90 ft. per sec., which is less than the tenth part of the velocity of sound in air;* * The volition and sensation move along the nerves at about the same rate as sound would be propagated in the nerve. The velocity of sound in Indiarubber softened is found to be 90 ft. per second. 2 196 ELEMENTS OF NATURAL HISTORY. whereas the velocity of the electric current is considered to be 10,000 times that of light, which is nearly 200,000 miles per second ! There can be no doubt that it is a chemical action that is propagated to and fro along the nerves, and that each message of volition and sensa- tion is accompa- nied by a che- mical change, and consequent loss of force that must be compensated for by fresh additions of new materials in the form of food. Branch nerves are given off by the spinal cord at each vertebra, and seve- ral of these pairs of nerves unite in the neck and loins, to form origins for the great brachial and sciatic nerves that supply the an- Fig. 114. terior and posterior limbs. The weight of the brain, as compared with that of the whole body, is as follows in several animals CKREBRO-SPINAL AND SYMPATHETIC NERVES. 1 97 Man, i to 40 Ox, , i. to 860 Elephant, Sheep, . . . Fox Mouse, . . . Green Monkey, to 500 to 350 to 205 to 43 to 40 to 27 Bonnet Monkey, . . . The cerebro-spinal system of nerves presides over what is called the animal life, including thought, sensation, and volition. (A.) Sympathetic System. This system of nerves presides over what is called the Organic or Vegetative life, and regulates digestion, respiration, circulation, and reproduction. It consists of two distinct parts, the ganglionic system and the great sympathetic; the former resembles, Fig. 109, the ner- vous system in the Molluscous animals, and is situated in great part in the cavities of the chest and belly, following the course of the blood vessels, whose rate of action it regu- lates. Its most important ganglion is called the solar plexus, which lies immediately behind the stomach, round the coaliac artery ; this great plexus is believed by some to be the seat of the nerve poisoning that constitutes the disease known as Asiatic Cholera. The great sympathetic consists of a number of double or knotted ganglions, arranged in pairs along the whole length of the vertebral column. There are three of these important ganglions in the neck, called the upper, middle, and lower cervical ganglions j these are in- timately associated with the tenth pair of nerves proceeding from the cerebro-spinal axis, and called the pneumogastric nerve, because, in conjunction with the cervical ganglions of the great sympathetic, it regulates respiration and diges- tion. Not only in the neck, but along the entire cord, the sympathetic and cerebro-spinal systems are united by means of interlacing filaments, so that throughout the entire body the most perfect harmony is kept up, during health, 198 ELEMENTS OF NATURAL HISTORY. Fig. 115.' between the motive principles of the animal and of the or- ganic life. C. Respiration. This func- tion is performed by means of lungs, I, ?, Fig. 115, which, with the heart, A, are placed in the cavity of the chest above the diaphragm; the external air enters the windpipe through the mouth or nose, and is dis- tributed by means of bronchial tubes through the substance of the lungs. In mammals, the bronchial tubes undergo a very minute subdivision, so that the venous blood pumped into the capillaries of the lungs by the right side of the heart, is forced into close contact with the fresh air distributed through the minute bronchial tubes, and so be- comes rapidly oxydised. The average amount of air contained in the lungs is 230 cubic inches, and of these, thirty cubic inches are renewed at each inspiration and expiration, so that at the end of eight breath- ings the whole air in the lungs is changed ; and as we make about sixteen inspirations in a minute, the whole air in the lungs is twice changed every minute. On examining the chemical com- position of the expired air, it is found to have gained four per cent, of carbonic acid, and to have lost a little more than four per cent, of oxygen. The carbon thus excreted from the body is esti- mated in the course of a day spent in usual labour, at 8 oz. or half a pound ; and it is believed that, in health, the lungs form the only exit for carbonic acid. The carbonic acid discharged from the lungs is really, like * Fig. 115 Lungs and heart of Man. I, /, the lungs ; A, the heart; tr, the trachea or windpipe ; vc, the vena cava inferior ; rf, the abdominal aorta. RESPIRATION. 199 other excretions, formed in the blood, and not in the lungs them- selves ; and its elimination is so necessary to life, that an immer- sion in water of sixty seconds will kill a man, although the lower animals will bear a longer immersion with impunity. In other words, the accumulation in the blood of the carbonic acid formed in one minute, corresponding to twice the contents of the lungs, will so poison the blood, that the brain ceases to act, and death ensues by coma. Inspiration and expiration are effected, partly by means of intercostal muscles, raising and lowering the ribs, and thus in- creasing or decreasing the cavity of the chest, and partly by means of the muscular diaphragm peculiar to mammals, which by its contraction enlarges the chest, and aids inspiration. We thus see how respiration in the animal kingdom is com- plementary to respiration in the vegetable world, and that they are mutually dependent on each other, alternately forming and unforming carbonic acid for each other's use. D. Circulation. The heart of mam- mals, Fig. 1 1 6, is double ; the right side consisting of two cavities, the right au- ricle ra, and the right ventricle rv, sepa- rated from each other by a large orifice called the auriculo- ventricular opening; and the left side consisting of two similar cavities, the left auricle la, and the left ventricle Iv, separated from each other by a similar auriculo-ventricular opening. ^S- "6.* The right auricle, ra, receives the blood from the entire body, poured into it by two large veins called superior vena cava, vcs, and inferior vena cava, vci; the venous blood, loaded with carbon, is passed from the right auricle into the right ventricle, the * Fig. 1 16 Diagrammatic Representation of the Heart, ra, rv, the right auricle and ventricle ; vcs, vci, the venae cavse ; xx, the pulmonary arteries ; la, Iv, the left auricle aad ventricle ; yy, the pulmonary veins ; aa, the aorta. 2OO ELEMENTS OF NATURAL HISTORY. walls of which are composed of a powerful muscular structure, which contracts and propels the blood from the heart into the lungs, through the pulmonary arteries xx, while it is prevented from passing back again into the right auricle, by a valvular structure consisting of three flaps, and called the IricuspiA valve ; the blood having un- dergone, by oxidation in the lungs, the change converting it from venous into ar- terial blood, is re- turned through the pulmonary veins, yy, yy, into the left au- ricle of the heart, la, from which it passes, in turn, into the left ventricle, Iv, composed of a muscular struc- ture more powerful even than that of the right ventricle ; by which it is propelled through the great aorta, which is shown at aa, Fig. 1 1 6, through the arteries of the whole body, as shown in Fig. 117, carrying Fig. 117. with it the elements of fresh nutrition to every minute part. The arterial blood is prevented from regurgitating into the left CIRCULATION. 2O1 auricle by a valvular structure, similar to that of the right au- riculo- ventricular opening, but consisting of only two flaps, whence it is called the bicuspid, or mitral valve. The openings of the pulmonary artery into the right ventricle, and of the great aorta into the left ventricle, are closed by three valves, called the semilunar valves, which, in health, prevent a single drop of blood from returning back into the heart, when the contraction of its ventricles has ceased. The walls of both ventricles contract simultaneously, pro- pelling the venous blood into the lungs, and the arterial blood through the arteries of the whole body ; when their contraction has ceased, the auricles contract in turn, but with much less force, upon the blood sent in by the vence cava, and by the pul- monary veins, and, by their contraction, refill the empty ventri- cles, which again contract as before ; and so the circulation, both in the lungs and in the body, is kept up by a system of pulsa- tions, rythmical in character, and differing in different animals, and at different periods of life. The form of the heart is various; it is broad in the cetaceans and elephant, elongate in the dog, and round in monkeys, while it is obtusely conical in the horse, ox, orang outan, and in man. Previous to birth, the pulmonary circulation provided by the right side of the heart is useless, and, consequently, the two au- ricles communicate before birth by an opening, which closes shortly after birth, leaving a scar or pit, called the foramen ovale : in seals and other animals that remain long under water, and re- quire less oxydation of their blood than other animals, the fora- men ovale remains sometimes open through life ; and in man, the same circumstance is occasionally observed, as the result of some congenital defect. In such cases, the mammal is partially re- duced to the condition of a lower form of vertebrate animal, and the oxydation of the blood is most imperfectly accomplished, a portion of the whole blood only being transmitted through the lungs at each pulsation. 202 ELEMENTS OF NATURAL HISTORY. The heart of man has been computed, in the course of a day, to give out a quantity of work equivalent to lifting 122 tons through one foot ; but both in man and animals its work varies with occupation and age ; thus, the hearts of cab horses are found to be more muscular and larger than those of dray horses worked at walking pace ; and it is well known that the heart of man grows heavier and more muscular with advancing years, because more and more work is thrown upon it by reason of the increasing rigidity of the arteries, which are less elastic than in youth. E. Digestion. Having considered the apparatus by which carbonic acid is excreted from the system, and the blood oxydised in the lungs ; and also the mechanism by which the entire blood is pumped perpetually through both lungs and body; it remains to examine briefly the process called digestion, in which may be included the excretions formed by the liver, by which certain elements, as hydrocarbons, are removed from the blood, and thrown out of the body, in a manner not unlike that in which carbonic acid was shown to be excreted by the action of the lungs. The food received by the mouth is passed into the stomach, and thence through the intestines, undergoing a variety of changes in its passage ; by means of which certain portions of it are ab- sorbed into the blood, and so form the fresh materials by which the tissues of the body are repaired. The order in which the parts of the alimentary canal, from the mouth downwards, or backwards, are arranged, is the following : a. Mouth. b. Pharynx and (Esophagus. c. Stomach. d. Duodenum. e. Small Intestines. /. Caecum. g. Colon and Rectum. The total length of the intestinal canal varies much in dif- ferent animals ; in Man it is usually 30 feet in length, and is DIGESTION. 203 longer in the herbivorous than in the carnivorous animals ; thus, in the Ox it is 150 feet in length, and in the Lion only 1 8 feet long. The length of the alimentary canal seems to depend also on its diameter ; for in the Jlyana, Seal, and Otter, which are carnivo- rous animals, although the canal is unusually long, yet it is re- markably narrow, so that the amount of absorbing surface, with which the food is brought in contact, is not really greater than in other carnivorous animals endowed with a smaller length of intestine. (0.) The Mouth. In the mouth of mammals, the food is sub- jected to the process of maceration by the salivary glands, and of mastication by the teeth. With the exception of the cetaceans, all mammals are provided with salivary glands, which are more highly developed in proportion as the food is subjected to a more or less prolonged mastication. In man, the salivary glands are three in number, at each side of the mouth, viz., theparotid, the submaxillary , and the sub- lingual glands. The secretions of these glands, in all mam- mals, consist of water, salts, mucus, and from one to two per cent, of a peculiar principle, called salivine, which has the property of converting the starch of the masticated food into sugar. (b.} The Pharynx and (Esophagus. The commencement of the alimentary canal, behind the mouth, consists of a wide mus- cular bag called the pharynx, which passes downwards into the narrower tube called the (esophagus, which, like the pharynx, is very muscular, and capable, by means of a ver- micular movement, of propelling the food, transmitted to it from the mouth, into the stomach. Its muscular coat, in most mammals, consists of two concentric portions, in which the muscular fibres are spirally arranged and run in opposite directions ; in Man, however, it consists of an external coat of longitudinal fibres, and an internal coat of transverse cir- cular fibres. The action of the pharynx and oesophagus 2 04 ELEMENTS OF NA T URA L HIS TOR Y. with respect to digestion is purely mechanical, as no secre- tion is poured into the food, except that of the salivary glands, before it reaches the stomach. The oesophagus pene- trates the diaphragm, and immediately afterwards enters (c.) The Stomach. The general arrangement of the sto- mach, and other organs of digestion, below the dia- phragm, are shown in Fig. 1 1 8, which is drawn from the Otter. In this diagram dd, represents diaphragm; III, different lobes of the liver; ss, ,, stomach; sp, spleen; k, ,, right kidney; 6, ,, urinary bladder; 9i ,, gall bladder. The internal coat of the stomach secretes, copiously, when food is introduced, a li- quid called gastric juice, the active principles of which are known as lactic acid and pep- sine. These substances, acting upon the nitrogenous parts of the food, such a&filrine, albu- men, and gelatine, convert them into a substance called peptone, capable of being assimilated when received into the blood. Thus, the special function of the salivary glands is to digest the starch compounds of the food ; and the special function of THE STOMACH, 205 the gastric juice is to digest the nitrogenous elements of the food ; the remaining, or fatty elements of food, are, in like man- ner, digested, and prepared for assimilation by the pancreatic juice. The form of the stomach differs much in different mammals ; in the kangaroos, it is elongate, and resembles a part of the large intestine ; and in some Bats, Monkeys, and Sloths, it is divided into several compartments by constrictions, but it is in the Ruminants that the stomach becomes really compound, and deserves par- ticular notice. In these animals, the first stomach, called the paunch, lies on the left side, terminates in two blind sacks, is very large, and is covered on the inner surface with horny papillae ; the second stomach, called the honeycomb, is much smaller, lies on the right side of the paunch ; it is round, and is covered on its inner surface with six-sided cells that give to it the name of honeycomb ; between thejirst and second stomach, the opening of the oesophagus is placed, so that the food descending from the mouth can be " shunted" at pleasure into either one or other stomach. On the right side of the honeycomb, lies the third stomach, called the many plies ; it is elongate and covered on the inside with many broad, longitudinal folds, arranged like the leaves of a book ;* the wanyplies, or third stomach, communicates with the honeycomb, or second stomach, by a narrow opening ; while it communicates with the reed, or fourth stomach, by means of a very wide opening ; the fourth stomach is of considerable size, and resembles in shape the stomach of Man, or of the Otter, shown in Fig. 1 18. It possesses longitudinal folds that secrete gastric juice, like ordi- nary stomachs ; and in the young animal, fed on milk, is the lar- gest and most important of the four. Daubenton proved, by * These leaves are of different sizes, as if books of different kinds had been bound together ; in the ox, there are ninety-six leaves in all ; twenty- four large, forty-eight small, and twenty-four of middle size. 206 ELEMENTS OF NATURAL HISTORY. feeding different lambs on grass and on milk, that the paunch remained undeveloped, so long as the milk food was used. The paunch may be regarded as a reservoir of food (similar to the buccal pouches of some monkeys), in which the store of food is macerated before being chewed ; and Ruminants possess the power of regurgitating the food from the paunch into the mouth, for mastication, at pleasure. The third and fourth stomachs, or manyplies and reed, are united into one, both in the Llama and in the Camel. It is remarkable that the juices secreted by the paunch and honeycomb are alkaline, like the saliva ; while those secreted by the manyplies and reed are acid, like the gastric juice. The food, masticated by the teeth, having had its starch con- verted into sugar by the saliva, and its nitrogenous parts con- verted into peptone by the gastric juice, is finally transferred as a pulpy mass called chyme through a muscular valve called the pylorus (TrvXwpd?) into the (d.} Duodenum, or commencement of the small intestines. The pancreas, or whiiebread, is a narrow flat gland, extending across the abdomen under the stomach ; and possesses a duct traversing the entire length of the gland; its secretion is poured into the duodenum, together with that of the liver, shortly below the pylorus, and possesses the special function of digesting the fatty portions of the food. This important fact is proved by many experiments on animals ; thus, in dogs from which the pancreas have been removed, the fat used in food is found to be passed, unaltered, on defecation ; and in patients suffering from diseases of the pancreas that destroy its action, the same phenomenon is observed ; and both dogs and patients rapidly grow thin, from the cessation of the pancreatic juice, which in health assimilates the fatty and oily constituents of the food. The pancreatic juice pos- sesses also the same action upon starch, that belongs to the saliva, so that any portions of starchy food that may have THE SMALL INTESTINES. 207 escaped conversion into sugar during the process of masti- cation are acted upon by the pancreas, and the process of conversion of starch into sugar completed. (e.} Small Intestines. The portions of the small intestines helow the duodenum are called the jejunum, and the ileum, which latter name continues as far as the ccecum, where the large intestines commence, and are usually separated from the small intestines hy a valve called the ileoccecal valve, which allows the contents of the small intestines to pass into the caecum, but prevents their return. Through the entire length of the small intestines absorption of the digested food takes place by the capillary lacteals ; and certain little known secretions are added to it by the surface of the intes- tines themselves. In order to increase the absorbing sur- face, the interior of the intestine is arranged in a series of valve-like folds, so as to bring the food into contact with as large an absorbing surface as possible. The digested food, in passing from the stomach, is called chyme (xt^os), and possesses an acid reaction, due to the excess of gastric juice ; when the chyme has received the secretion of the pancreas, and the excretion of the liver (bile), it acquires a slightly alkaline reaction which it retains through the whole of the small intestines, and is called chyle (x^Xo's) ; it owes its alkalinity to the bile, which possesses a feebly alkaline reaction. (/.) The Ccecum, as the name implies, is a blind cul de sac, placed at the commencement of the large intestines, and the food which has passed the ileoccecal valve is subjected in the ccecum to a second coction, which has been compared to a second stomachal digestion. The surface of the ccecum se- cretes an acid juice, which counteracts the alkalinity of the chyle, and also secretes the oils that give to the fa3ces of each animal their characteristic odour. The ccecum of different kinds of mammals is very different, 208 ELEMENTS OF NATURAL HISTORY. and it is therefore of much value in classification. One of the Anteaters, like the birds, possesses two caeca ; in Hyrax there is a short wide caecum, in the usual position, while lower down, in the large intestine, there are two other blind and conical ap- pendages placed side by side. (g.} The Colon and Rectum. The large intestine is divided into the ascending, transverse, and descending Colon, and the Rectum; shown, diagrammatically, in Fig. 119. Ascending Colon, A. Transverse Colon, . , . . T. Descending Colon, . . . . D. Rectum, R. Stomach, S. Duodenum, d. d. Small intestines, I. Caecum, C. Vermiform appendix of caecum, v . a. The longitudinal muscular fibres of the colon are arranged into three bands, which are shorter than the walls of the intestine itself, so that the latter is thrown into puckers and pouches ; and in the rectum, there is a remarkable ar- rangement of the circular fibres at the Fig. 119. termination of the gut, well known as the sphincter muscle, which keeps the aperture firmly closed, except when defecation takes place. It must not be supposed that all absorption of food ceases with the small intestines, although as a rule it does so ; for many instances are on record as, for example, in cases of closure of the oesophagus of persons having been kept alive for months by injections of warm milk and calf's head soup into the colon, when it was impossible to administer food in any other way. F. The Liver and Kidneys. The liver constitutes the largest THE LIVER AND KIDNEYS. 209 gland in the bodies of most animals, and serves a double pur- pose that of forming a secretion necessary to the complete di- gestion of the food, and an excretion of hydro-carbons from the blood. It is situated below the diaphragm, Fig. 1 18, II, chiefly on the right side, and is sometimes divided into lobes, as in the carnivorous animals; the secretion of the liver, called bile, is in many animals collected into a gall bladder ; but this organ is often wanting, as in the Whale, the Elephant, the Sloth, and the Deer. The bile ducts open into the duodenum at the same place as the pancreatic duct, and the two secretions seem to act simultaneously on the chyme poured out from the stomach. Bile is found to consist principally of biline, composed essentially of two organic acids, Taurocholic and Glycocholic, one of which contains sulphur and the other does not ; and of a peculiar crys- tallized fatty substance called cholesterine, which forms the sub- stance of gall stones : in addition to biline and cholesterine, the bile contains water, saline, and colouring matters, which, with the cholesterine, are to be regarded as excretions, while the biline is to be regarded as a secretion necessary to digestion. Cholesterine, and the salts of bile are found in the blood, just as the carbonic acid excreted by the lungs, and the urea excreted by the kidneys are found in the same fluid ; hence, so far as these substances are concerned, the liver plays the part of a simple excreting organ, separating from the blood, substances pre-existing in it, and rejecting them from the body. The total quantity of bile excreted by & healthy man in twenty-four hours is estimated at something under 4.0 oz. (16940 grs.); of which 10.4.69 grs. are pure cholesterine, and have been found by direct experiment to be represented by 10.417 grs. of stercorine actually discharged" from the body. The quantity of biline secreted by the liver in one day, cor- responding to the 10 grs. of cholesterine excreted, amounts to 1 345 grs., the whole of which is employed in modifying the pro- ducts of digestion, and in forming chyle, and is again re- absorbed 210 ELEMENTS OF NATURAL HISTORY. from the intestinal surface, and reintroduced into the blood. The liver is supplied both with arterial and venous blood, and performs, as we have seen, the double function of secretion and of excretion. Biline is not found in the blood, and is therefore to be regarded as a pure secretion, formed by the liver itself. It is a remarkable fact, that the blood that leaves the liver after the elements of biline and cholesterine have been abstracted from it, contains a larger quantity of sugar than the blood that enters it ; as if the sugar also (glucose] were a prodiict of the chemical changes that produced the proper secretions of the liver. The Kidneys, in mammals, are situated in the lumbar region, Fig. 1 1 8 &, outside and behind the sack that contains the intes- tines. In many mammals the right kidney is higher up than the left, but in man the reverse is observed ; they are surrounded by a loose areolar tissue in which much fat is accumulated, highly prized by gourmands. In the human embryon, the kidneys con- sist of several masses or lobes, and in some animals they continue in this condition through life, as in the Seal and Bear. It is the special function of the kidneys to excrete nitrogen, in the form of the compound called urea ; just as it is the function of the lungs to excrete carbon in the form of the compound called carbonic acid. The daily excretion of urine in man is about 40 oz., or the same as the secretion of bile ; and these 40 oz. of urine contain 500 grs. of urea, having the composition Two atoms of Carbon, . . 1 2 . . 20 per cent. Four atoms of Hydrogen, . 4 . . 6$ Two atoms of Nitrogen, . 28 . . 46! ,, Two atoms of Oxygen, . . 16 . . 26| 60 too The importance of the due excretion of urea cannot be exagge- rated, for it forms practically the only outlet for the nitrogen that constitutes so large a portion of our food, and its retention in the CLASSIFICA TION OF MAMMALS. 2 I I body is quickly followed by coma and death ; less rapid only than that which follows the retention of carbonic acid. There are three, and only three, excretions of Mammals essential to life and health : viz. water, carbonic acid, and urea ; of these, water is excreted by the lungs, kidneys, and skin ; car- bonic acid is excreted by the lungs ; and urea, by the kidneys. It is only for a short period, and then near the close of life, that any of these organs can take upon itself the functions of the others : when this occurs, unless the cause of the derangement be tem- porary, death shortly closes the scene, and stamps with his seal the unchangeable fiat of the Creator. 3 . Classification of Mammals. Mammals are divided into two great subdivisions i. Placental Mammals, n. Non- Placental Mammals. In all mammals of the placenta! class the young is nourished in the womb of its mother by means of a remarkable structure called the placenta, which consists of very vascular tissue, in which the arterial blood provided by the circulation of the mother, is passed through minute capillary vessels that increase in size like veins, before they unite to enter the circulation of the young. The young of placental mammals are thus nourished with the mother's arterial blood, until, when born, they are able to seek their nourishment, by sucking the mother's teats. In \henonplacental mammals, on the other hand, the young are not nourished by a placenta in the womb, but are born in an immature condition, and fastened by the mother herself upon the teat, which they are unable to suck by their own eiforts ; and therefore the milk is squeezed, by a muscular exertion on the part of the mother, into the mouth of the young until mature. It is also noticeable that the supplying of the young with milk, is not left merely to an instinct of the mother, but is effected also, involuntarily, by each movement of 2 I 2 ELEMENTS OF NATURAL HISTORY. the hind limbs. The placental Mammals are divided into the following orders : I. Placental Mammals. A. Man. B. Quadrumans . . C. Chiropters. D. Carnivores . . . E. Insectivores. F. Ungulates . . . G. Rodents. H. Mutilates ... I. Edentates. A. MAN. Has the incisor, canine, and molar teeth even, con- tiguous ; molars equally enamelled ; incisors four in each jaw. Feet five-toed, anterior limbs furnished with five-fingered hands ; nails all fiat, broad. Gait erect. Placenta deciduate, discoidal. Man is distinguished from all animals by his moral and rea- soning faculties, but, anatomically, the distinction between man and the lower animals is much less than his moral and intellec- tual superiority would lead us to expect. He possesses an erect gait, such as is unknown even among the highest monkeys, and this circumstance sets free his hands to minister to his intellectual wants, instead of being used as instruments of locomotion. The articulate speech of man, based upon the universal laws of gram- mar, is the simplest exponent of his reason ; and through means of speech man possesses traditions and a history, and becomes capable of progressive improvement in civilization. Blumenbach considers that there are five races of men Caucasian, Mongo- lian, vEthiopic, American, and Malay and most naturalists be- lieve (independently of tradition) that the differences between these races are not sufficient to entitle them to be regarded as distinct species. B. QUADEUMANS. Possess incisor, canine, and molar teeth; molars equally enamelled. Feet unguiculate, either all pentadacty- lous or only the posterior, with anterior tetradactylous. Thumb in the pentadactylous feet remote from the other fingers, with nail fiat. Pectoral mammte. Placenta deciduate, discoidal, lobate. These animals include the monkeys, apes, &c., animals which QUADRUMANS. 2 1 3 are called quadrumanous, because their hind feet grasp objects in climbing, after the manner of hands ; thus they are four- handed mammals. The whole order is intended to live in trees in tropical regions, a mode of life, for which the structure of their feet, and the prehensile tails of many of them peculiarly adapt them. They are found in the forests and rocky deserts of Southern Asia, Africa, and South America, where they live in troops, and feed principally on fruits. It is remarkable, that while the teeth of most of the monkeys of the Old World agree in number with those of man, the monkeys of the JN^ew World have three false molars, instead of two, at each side of each jaw. The Quadrumans differ remarkably from man in the action of their feet, having free thumbs opposable to the other toes, which are long and slender, like the fingers of the hand. They therefore climb branches of trees with facility, but cannot stand or walk erect without much difficulty, for in this position the soles of the feet are nearly opposed to each other, and the feet rest on their outer edges, while the narrow pelvis is very un- favourable to equilibrium in the erect posture. The intestines and viscera of the quadrumans, with some exceptions, are similar to those of man so much so, that several of the descriptions of Galen, founded on the dissection of Barbary Apes, have been sup- posed to be taken from the human body. The brain of the higher monkeys is very like that of man so, like indeed, as to demon- strate how little we know of the real connexion between the brain and the intellect, of which it is the instrument ; for no anatomical evidence exists to explain the profound difference be- tween these animals and man. The Quadrumans include the following sub- orders : i. Strepsirhine Quadrumans, having twisted or curved terminal nostrils, and the second toe of the foot converted into a claw. Example The Lemur Madagascar. The Lemurs inhabit Madagascar, and a few of the smaller islands in its vicinity, in which they fill the place of monkeys, 2 14 ELEMENTS OF NATURAL HISTORY. none of which exist in Madagascar. They live, like the monkeys, in troops upon the trees, and feed upon fruits and insects. In captivity they are very affectionate and good- tempered, fond of being noticed, and exceedingly active, leaping from point to point, alighting without noise. They are nocturnal in habit, and pass a considerable part of the,day in sleep. When two of these animals are confined together, they interlace their legs and tails in a singular fashion, placing their heads so that each can see, if disturbed, what takes place behind his neighbour's back, and so they take their diurnal nap. 2. Platyrhine Quadrumans, having the nostrils subterminal and wide apart, the thumb of the hand not opposable or want- ing, and the tail prehensile. Example the Capuchin Mon- key South America. The Capuchin Monkeys, or Sapajous,* live in the forests of South America, and differ from the monkeys of the Old World in the number of their pre-molar teeth, and in their prehensile tails. Their hands are inferior to those of the other mon- keys, because the thumb is not opposable to the fingers ; they are small in siae, and playful in disposition, and lead a merry life, springing in flocks from tree to tree, and feeding upon fruits, insects, and eggs of small birds, of which they are the natural enemies. The species called Capuchin has a black hood of hair round its face, and has a habit of crossing its long arms upon its breast, as if in the attitude of prayer, from which habit it has received the name of Ca- puchin Monkey. 3. The Catarrhine Quadrumans, with oblique nostrils and approxi- mated below, opening above and behind the muzzle; thumb of hand opposable. Examples Baboon Africa and Asia. This sub-family of Quadrumans inhabits the Old World, * These are believed to be the happiest animals that God has created. THE CHEIROPTERS. 2I 5 and agrees with man in many points of structure ; it also includes the celebrated anthropomorphous apes, Gorilla, Orang Outang, and Chimpanzee. Of these, the faces of the Orang and Chim- panzee are very human, while young, hut lose this character as age advances, in consequence of the growth of the bony ridge, to which the temporal muscles are attached, which close the jaw ; the growth of these ridges gives a savage and ferocious expression to the adults of all the Catarrhine Apes, the males of which have large canines to match their temporal muscles ; and are, as a class, much less gentle and playful than the innocent Lemurs and Capuchins. C. THE CHIBOPTEES. Incisor teeth various in number; canines distinct; molars uniformly enamelled, multicuspidate or furnished with crown depressed. Feet Jive-toed. Bones of arms and fingers elongate, sustaining a large membrane serving as a wing for flight ; fingers, except thumb, furnished with claws ; toes short, all furnished with claws. Two pectoral mammce. Placenta deciduate, discoidal. The Bats, or wing-handed mammals, form a very natural group, and are so named from the elongation of four fingers of the hand, for they fly by means of the membrane attached between the ex- Fig. 120. tended fingers of the hand, Fig. 120, while the thumb remains of the ordinary size. Although their hands are chiefly devoted to 2l6 ELEMENTS OF NATURAL HISTORY. the purpose of flight, yet they are capable of prehension as well, and in this respect are superior to the wings of birds, which are used for flying only. Their eyes are small, and ears large, be- cause they are nocturnal animals, and they derive their ancient name ( Vespertilio] from this circumstance lucemque perosae Nocte volant, seroque trahunt a vespere nomen. They resemble man and the quadrumans in the structure of their placenta, and produce one or two at a birth, which are of very large size in comparison with the parent. They all possess clavicles, but the forearm does not admit of rotation, as this would interfere with the steadiness required for its use as a wing. They possess no caecum at the commencement of the ascending colon. The bats are divisible into two very natural groups 1. The insectivorous bats. 2. The frugivorous bats. These two groups are remarkably distinguished from each other, by characters suited to their different kinds of food, and the different habits required for procuring it. Thus, the intes- tinal canal in the frugivorous bats is seven times the length of the body, while in the insectivorous bats it is only twice that length. Also in the insectivorous bats the clavicle, and the portion of the sternum with which it articulates, are much more developed than in the frugivorous bats, who require a power of flight sufficient to carry them from tree to tree only, and are not required to follow the rapidly changing flight of insects pursued for food. D. THE CARNIVOKES. Incisor teeth, generally six in each jaw ; molars uniformly enamelled, with acute uneven crowns ; one or more of the hinder teeth tuberculate. Toes mostly cloven ; thumb not sepa- rate from the other toes or fingers. Placenta deciduate, zonular. The Bengal Tiger, drawn from the life in Fig. 121, may be regarded as the type of the large Cats, which are the most highly organized of all the Carnivores. THE LARGE CATS. 2I 7 These mammals live mostly on animal food, some exclusively ; a few of them eat fruits also, and other vegetable matters. Their Fig. 121. motions are rapid, and irritability great ; many possess uncommon muscular power. Their organs of sight and smell are peculiarly developed. They are divided into three groups, viz. a. Digitigrade. b. Plantigrade. c. Pinnigrade. (a). Digitigrade carnivores, or walking on the toes without bring- ing the heel to the ground. Examples Otter, Dog, Cat. This important division includes the Cats proper, Civets, Hyanas, Dogs, Otters, Skunks, Polecats, and Martens. Some of the Digitigrade Carnivores are provided with only one blunt molar behind the lacerator (dent carnassier}, and form a very natural group, commonly called vermin including the Polecat, Weasel, Ferret, Ermine, Marten, Skunk, and Otter. The Otters, as all know, are aquatic in their habits, and live upon fish and crustaceans; they bring their prey ashore to be devoured, and when fish is scarce, they have been known to attack and destroy lambs. They inhabit sequestered nooks at the river side, and are nocturual in their habits, like many other beasts of prey. 2 1 8 ELEMENTS OF NATURAL HISTORY. Another group of Digitigrade Carnivores, of which the Dog is the type, is characterized by having two blunt molars behind the lacerator of the upper jaw. This group includes Dogs, Wolves, Foxes, Civets, and Ichneumons. This latter animal was formerly worshipped in Egypt, on account of the services it rendered, by destroying the eggs of the crocodile ; and it is still employed in India, as a domestic pet to destroy mice, rats, and small serpents. It readily attacks and kills the deadly Cobra di capello* The Ichneumon has the pupil of the eye elongated transversely, like that of a goat. Dogs, Foxes, and Wolves, are closely re- lated to each other, and some naturalists have regarded them as descended from a common ancestor ; the fox is more remote from the dog and wolf than these are from each other, for the dog and wolf will breed together, while the fox and dog will not ; their period of gestation is identical, viz. sixty-three days ; the fox also differs from the dog and wolf in the form of the pupil of the eye, which in daylight closes into a vertical slit, like the pupil of a cat's eye. The Civets form a link between the cats and dogs ; and like the cats, their tongue is rough, and their claws retracted whilst walking, so that they are always sharp. The remaining digitigrade carnivores are distinguished by having no molar teeth behind the lacerator tooth of the lower jaw; this group contains the Cats proper and the Hyasnas. The Cats have five fingers and four toes, and claws retractile * Aristotle, in his History of Animals (ix. 7), thus describes the manner in which the Ichneumon was supposed to destroy the asps in Egypt : " The Egyptian Ichneumon, when it sees the snake called the asp, does not set upon it without summoning its companions to its aid ; these plaister themselves with mud as a protection against its blows and bites, and they accomplish this by wetting themselves and then rolling on the ground." The Ichneumon has improved since Aristotle wrote, and now attacks the Cobra without any such formalities ; he watches the moment when the snake poises its head to strike, seizes him by the throat, cracks his neck, and sucks his blood. LION AND TIGER. 219 or semi-retractile, and include the most active and largest of the Carnivores. The lion is the most powerful of the cats, and be- longs to the Old World ; it is now found in Africa and Asia only, but in former times it abounded in Europe, and so late as the time of Xerxes, these animals were so numerous as to attack the camels of his baggage trains. The lioness carries her young only three months, and has been known to produce two broods of four and five each, in a single year, in the Zoological Gardens of Dublin ; the cubs come into the world marked with dark stripes, and spots like those of a leopard ; both these kinds of markings dis- appear from the adult hide. The lion is said to prefer the flesh of the camel to that of all other animals, while the tiger is known to give a preference, like the leopard and crocodile, to the flesh of man himself. Notwithstanding all that has been said of the noble qualities of the lion, it must be confessed that he is a coward as compared with the tiger, and always attacks the smallest and weakest animal he can procure ; the royal beast owes much of his high reputation to his imposing main of long hair. He never attacks man without provocation, as the tiger will, who has been known in India to attack a file of horse soldiers on the march, and having snatched one from his saddle, to carry him off into the recesses of the jungle, without the possibility of rescue. The Puma and Jaguar of the New World may be regarded as the representatives of the Lion and Tiger of the Old World. The Hyaena occupies a position intermediate between the Dogs and Cats ; its claws are not retractile, but resemble those of the dog, except that it possesses only four fingers, as well as four toes. The fore limbs of the Hyaena are so much larger than the hind limbs, in proportion, that the animal has the appearance of dragging the hind legs after him, which gives a singularly re- pulsive aspect to the gait of this animal. They are nocturnal in habit, frequenting caverns and old ruins, and are very voracious, 220 ELEMENTS OF NATURAL HISTORY. possessing jaws powerful enough to crack the shin bone of an ox, which is a feat beyond the powers of the lion or of the tiger. (b.} Plantigrade Carnivores, or having the sole of the feet resting on the ground in walking. Examples Bear, Racoon, Badger. The Virginian Bear, drawn in Fig. 122, may be taken as a type of the Plantigrades. The animals included in this division of the carnivores are less carnivorous in their habits than the digitigrade Fig. 122. carnivores, and many of them, as the Bear and Badger, are ca- pable of living upon vegetable food, as honey, roots, biscuits, &c. ; some of the bears never eat flesh by choice. The Bear has the same number and kinds of teeth as the Dog ; the true molars are large and blunt, persistent, while the small pre-molars tend to disappear, after modes which vary among the several species. They have five fingers and five toes, and stand upon the hind legs in a manner more human than any ape is capable of doing ; this peculiarity chiefly arises from the form of the thigh bone, which has been fre- quently mistaken for a human bone, by geologists not skilled in comparative anatomy. The white bear is the largest and fiercest of the plantigrade carnivores ; it lives in the frozen regions of the north, and feeds on fishes, seals, and young whales ; in confinement, however, it can be brought to feed largely, like other bears, on biscuits and other vegetable food, and it delights especially in a meal of omental fat. PINNIGRADE CARNIVORES. 221 Pinnigrade Carnivores, or swimming by means of fin-like paddles. Examples Seal, Walrus. The Seal (Phoca vitulina), shown in Figs. 112, 123, and 1 24, may be taken as the type of the Pinnigrades. These carnivores inhabit the water, and have four or six upper incisors ; lower incisors four or two ; the hands and Fig- 123- feet are palmate, pentadactylous ; the feet turned back- wards and approximated to each other ; the fin-shaped hind Fig. 124. feet are blended into one screw- shaped organ with the flattened tail ; and the propulsion of the animal through the water is effected by the screw motion of the hind feet and tail, reversed at every stroke ; special arrangements of the muscles of the hind legs are made to suit this screwing action, which is so different from ordinary locomotion on land. The fore feet of the seal are not used in swimming, 222 ELEMENTS OF NATURAL HISTORY. towards which action they contribute as little as do the fins of a fish. * The Seals live in various seas, and are very numerous in species, especially in both the polar regions ; they delight to sun themselves upon rocks, but their motions on land are awkward, resembling the vermicular motion of a caterpillar ; they bark like a dog, and possess much intelligence, having a very large brain; the sense of touch is developed in an unusual manner, by means of the fifth pair of nerves, distributed to large bristles that surround the muzzle, which are supposed to guide the animal by touch under water ; the nerves supplying these bristles are so large and important, that a blow of a stick upon the muzzle will kill a seal, from the nervous shock carried to the brain. E. THE INSECTIVORES. Incisor teeth various in number, and not seldom different in the two jaws ; no true canines in many species, false molars with double roots occupying their place ; molar teeth with conical-pointed tubercles; feet plantigrade, often Jive- toed. Placenta deciduate, discoidal. The Mole, drawn in Fig. 125, may be regarded as a type of the Insectivores. S/ij* ^^= -^^== - Fig 125- The British Isles possess three examples of the Insectivores ; viz., the Mole, the Hedgehog, and the Shrew, which render much service to the husbandman, by destroying insects and grubs, THE IXSECTIVORES. 223 the multiplication of which would prove destructive to his crops. The British farmer repays this kindness by accusing the Hedgehog of eating his apples, the Shrew of biting his horses, and the Mole of spoiling his land. The Hedgehog is covered with spines instead of hairs, and has the muscles of the skin largely developed, by means of which he is able to roll himself into a ball, and so set his numerous ene- mies at defiance. This animal is endowed with extreme sensi- tiveness to moisture, and the following statement of Aristotle (History of Animals, ix. 7) is still regarded as correct : "Respecting the sensitiveness of hedgehogs, it has been often observed, when the north and south winds are interchanged, that hedgehogs in the ground will change the openings of their burrows, and that those reared in the house, will change from wall to wall ; and it is related that a man in Byzantium acquired the character of a weather prophet, by observing these habits of the hedgehog." The Mole, Fig. 125, lives a subterranean life, for which he is admirably adapted by his structure. The fore limbs are very short, and mounted on a scapular arch of strong construction; they are worked by muscles of unusual strength, and terminated by broad hands, furnished with short fingers, and long spade-like claws, turning slightly outwards. The hind legs are feeble, and the motions of the animal on the ground are as awkward as they are active beneath it. Its hearing is very acute, but its eyes are re- duced to mere points, so that it can, probably, barely distinguish the day from the night. The Mole is remarkable for its domestic attachments, and for the care it takes in providing for its young. It feeds chiefly upon worms and grubs, and is fond of certain roots, such as the crocus, on which it feeds its young; for this reason, it is no favourite with gardeners. The Shrew, or field mouse, has a general resemblance to the mouse, but is essentially a different animal ; it readily takes the water, and swims and dives with ease ; it is a most inoffensive 224. ELEMENTS OF X AT URAL HISTORY. animal, and lives exclusively on worms and insects. Aristotle is answerable, to some extent, for the prejudice entertained against this innocent beast, for he says (Hist. Animals, viii. 23), " The bite of the shrew mouse is injurious to other animals, as well as to the horse ; it causes sores, which are more severe if it is pregnant when it bites, for the sores then break ; if they are not pregnant, the animal does not perish." The Shrew is one of the smallest of mammals, measuring only 2^ inches in length. F. THE UNGULATES. Feet hoofed; unfit for grasping, and of low tactile sense ; the limbs restricted in use to support of body and locomotion ; molars with broad summits for grinding vegetable food. No clavicles. Placenta either diffuse, or arranged in cup- shaped masses (cotyledons). This important Order of herbivorous mammals is divided into two sub-orders, according as the number of the fingers is even or odd. (a.) Even-toed Ungulates have nineteen lumbodorsal vertebra ; horns, if any, in pairs; they are divided into the two groups 1. Ruminants, that chew the cud. Examples Deer, Camel, Giraffe. 2. Omnivores, as the Pig, Hippopotamus. i. The Ruminants, feet bisulcate, with two toes insistent, un- gulate, two supplementary hoofs in many. Molar teeth complex, upper incisors mostly none, lower eight, more rarely six ; canines mostly none. Four, or three stomachs. Metacarpal and metatarsal bone single, bipartite below. This important sub-order of animals is of the greatest use to man, and has been known to him from time immemorial. Moses correctly distinguishes the Euminants from the Omnivores, by stat- ing that a true ruminant must both "chew the cud," and " divide the hoof/' and he therefore excludes the Pig from this sub-family. Some ruminant animals have horns, and others have not; among those not provided with horns, the most important are, the Camel, and its representative in the New World, the Llama. THE CAMELS. 225 The Llamas are illustrated by Fig. 126, which shows the head of the Guanaco ; and Fig. 1 27, which shows the foot of the Llama proper. Fig. 126. Fig. 127. The Camel and Llama are distinguished from other ruminants, as well by their hoofs as by the possession of incisor teeth in the upper jaw ; these teeth arise from the inter-maxillary bone ; they are close to the canines, and agree with them in form. Their feet are callous beneath, with undivided sole, didactylous, with- out supplementary hoofs. The Camelidce form a connecting link between the ruminants and the other ungulates, by having six incisors in the upper jaw, and by the fact, that their placenta is diffuse, and not composed of cotyledons, or cup-shaped masses. They have the upper lip cloven, and the neck very long. The Camel derives its name from the Hebrew tongue ; it feeds on dry or prickly plants, and drinks seldom. They are rapid in their course, and bear large burdens, from 600 to i ooo Ibs. ; hence they are of great service in the deserts which stretch from Arabia, through sub-central Africa, to the Atlantic Ocean, where no fresh plants cool the air, no fountain gives fertility, and the wind blowing in arid whirlpools, causes interminable oceans of sand 226 ELEMENTS OF NATURAL HISTORY. and dust. The Arabs have properly named this valuable animal " The ship of the desert." "Within the last year, 1866, the Camel has been used in Australia, in an expedition across the deserts of that country, and has proved itself, as in Africa and the East, in every respect superior to the horse. There are two species known, distinguishable from each other by having one or two humps upon the back ; that with one hump is called the Dromedary, or Arabian Camel, and that with two humps is called the Bactrian Camel. The Llama in South America represents the Camel of the Old World, but is very inferior to the camel in strength and size ; they are employed as carriers, but their usual load is only 150 Ibs. ; and they are not capable of the rapid motion of the Dromedary, which has often accomplished 100 miles a day for several days, with a man upon his back. There are several species known, of which the Llama proper, and the Vicuna, are highly prized for their wool. The ruminants furnished with horns are so well known, that a minute description of them is quite unnecessary. The horned ruminants may be thus classified ; ruminants having 1. Horns always under the skin (Giraffe). 2. Horns permanent, hollow (Cow). 3. Horns deciduous, or antlers (Deer). The Giraffe has two frontal horns in both sexes, conical and truncated, short, covered with hairy skin, and persistent; its neck is very long ; the fore feet longer than the hind feet, like the Hysena. The Giraffe is the tallest of mammals ; when stand- ing up, its height is 1 6 to 1 8 feet ; its tongue is long, and pos- sessed of great mobility, and is used by the animal to strip from trees the leaves on which it feeds, which are chiefly those of the Mimosae. The Giraffe also grazes without kneeling, with the fore feet widely straddling ; in its flight it gallops with the fore legs stiff, in rising and falling ; at other times it has an ambling gait. THE HORNED RUMINANTS. 227 Its period of gestation is fourteen months, and the young is very large at birth. The Giraffe is a native of Nubia and Abyssinia, and is also found in South Africa. In its anatomical structure it is more closely related to the Deer than to the Antelope. The gigantic fossil ruminant, called Sivatherium, found on the flanks of the Himalayahs, is supposed to have been allied to the Giraffe. The hollow-horned ruminants are provided in both sexes, or in the male only, with double horns, composed of a bony nucleus and a horny sheath persistent ; there are accessory hoofs in many ; no incisors in upper jaw, six incisors in lower ; no upper canines ; molars six in each jaw ; or oo o-o 6-6 _ ^ 3-3 i - i 6-6 The horns consist of a bony core, and a horny case covering the bone ; the horny covering is produced by the surface of the core, and is composed of hairs concreted into a horny substance, of which a new ring is formed each year, as may be seen on ex- amination of a cow's horn. In many of these animals the bony core is itself hollow, as in the Cow and Goat, but in others, as the Antelope, the bony core is solid ; this, however, is but a small difference, and the whole group was justly regarded by Linnffius as one of the most natural in the Animal Kingdom. It may be divided into the four genera, Antelope, Goat, Sheep, Ox. The Antelopes are most numerous in Africa, in the southern part of which they abound ; many species present external re- semblances to the Deer, others to the Goat, some to the Ox, and some even to the Ass ; in all, the eyes are placed higher and more backward than in the Deer, and the base of the horns is mostly placed forward over the margin of the orbit of the eye, and the bones of the nose are usually very long. The Goats have horns in both sexes, flat on the inside, curved, annulate, and often knotted ; they live in troops in the mountains, and have very acute senses ; the domestic goat has a sharp edge Q 2 228 ELEMENTS OF NATURAL HISTORY. at the inner side of the horn, which is irregularly incised, and sometimes very broad. The Sheep was originally, when wild, an inhabitant of hilly countries, and therefore thrives well in high and dry regions > and is one of the most useful of the animals that man has tamed. The Sheep possess horns, in one or both sexes, wavily striated, transverse at the base, turned backward, with the tip mostly again bent forward. There are many varieties, among which may be mentioned the merino sheep, celebrated for its fine wool ; the Astracan sheep, noted for the curly fleece of the lambs ; and the Iceland and Syrian sheep, remarkable for their four or six horns. The Oxen have horns round either throughout, or towards the tip, turned outwards, incurved at the tip, ascending ; and are distinguished, by having four teats, from the goat and sheep, which have only two. The varieties of oxen are geogra- phically widely distributed, but it is remarkable that South America has produced no original wild species. The common Ox may live to twenty or twenty-five years ; and the period of gestation of the cow is 280 days ; the calf is born with cutting teeth and three molars in each jaw on both sides. The varieties of the ox are fewer than of the sheep ; among them may be mentioned, the Zebu of India, provided with a delicious hump upon his shoulders ; the Bison, in which the horns are si- tuated in front of the sharp line which divides the forehead from the descending part of the skull : the Buffalo has the horns directed outwards, and with a longitudinal projecting line; its native country is India, from whence it was introduced into Italy in the seventh century ; lastly the Musk ox, inhabiting the sub- arctic regions of North America, has a hairy muzzle, the horns approach each other at the base, and then proceed outwards and downwards, the point turning up again nearly as in the Gnu, which is the wild ox of Southern Africa. The last division of the Ruminants contains the Deer, the males THE DEER. 229 of which shed their horns each year ; many of them have canine teeth in the upper jaw. The Sambur Deer (Cervm Aristotelis) of India, whose head and foot are shown in Figs. 128, 129, may be regarded as a type of this group of Ruminants. The deers live principally in forests, both in the Old and New Worlds, and in very different climates ; from Africa only one* species is known, and not one from Australia. Most of them run with speed, and so lightly, that the beat of their feet upon the ground is not heard. The horns Fig. izS. Fig. 129. of the deer are bony excrescences which are developed on cylindri- cal processes of the frontal bones called the Rosestocks. The rose- stock is covered with skin and hair, and forms, when the animal is born, a bone distinct from the frontal bone ; with the rosestock of the true deer the horns of the giraffe correspond. The horns grow * Cervus Barbarus is the only species peculiar to Africa. Besides this and the fallow deer, there is an Algerian variety of the stag (Cervus Elaphus}. 230 ELEMENTS OF NATURAL HISTORY. each year from the rosestock very rapidly, so that in a few weeks they attain their full size ; the earthy part of some, as the Cervus megaceros, amounting to eighty Ibs. At first they are covered by a woolly investment or skin, and afterwards the skin dies and falls from the horns in shreds. The horns are cast in the same season in which they grow. The females, with the ex- ception of the raindeer, and perhaps the Cervus megaceros, have no horns. Among the most interesting varieties of the deer may be mentioned : the Elk, which is the largest living deer, and almost equals the horse in size ; it has large flat palmate horns, and is found in the northern parts of the Old and New Worlds ; the Reindeer, which inhabits the regions north of the district of the elk, and constitutes the chief wealth of the Laplanders, who by means of it, supply all their wants of clothing, food, and fur- niture ; the Fallow deer, which is spread by the influence of man over many countries, and is naturally wild in Italy, Spain, and North Africa : the Red deer is easily known by its rounded horns. One of the smallest species of deer is the Muntjac of Java and Sumatra ; it has large rosetocks and small horns, with canines in the upper jaw, projecting from the mouth in the male. 2. The Omnivores. The even-toed ungulates are divided, as already stated, into the Ruminants and the Omnivores, or as they might be named ruminant and non-ruminant. The non-ruminant even-toed ungulates, or omnivores, contain two divisions, the Pigs and the Hippopotamus, and they differ from all the odd-toed un- gulates, in not having a third trochanter, or prominence, deve- loped on the back of the femur;* the stomach, although not multiple, as in the ruminants, is complex, the ca3cum is smaller, and the colon is spirally folded. The Pigs have feet with the hoofs insistent, tetradactylous, * This is a distinction more apparent than real, for the muscle to which the trochanter belongs is found in the Cow and Pig, as well as in the Rhinoce- ros, Horse, and others. THE EVEN-TOED PACHYDERMS. 231 the hinder sometimes tridactylous ; nose with snout truncate, moveable, prominent ; tail short, or a tubercle in place of tail. In addition to the true hogs($ws) this family contains the Peccary of America, and the Wart hog of Africa, which differ in some parti- culars from the common hog. The Wild hog lives in the forests of Asia and Europe, and is an exceedingly voracious and prolific animal, producing from ten to fourteen at a birth ; near Upsala, a variety with a single hoof is found, as also in Hungary ; and there are many varieties found in Mexico, the Moluccas, Japan, and other places, but not worthy of being regarded as distinct species. The Hippopotamus has short tetradactylous feet, with short hoofs ; body obese, covered with skin almost devoid of hair ; it has the following dentition : I. 1^1 C . ' 1 M. 6 ^4 2-2 I - I 6-6 the lower incisors are procumbent, horizontal ; the canines large, worn obliquely into a very smooth surface at the back part ; the molars are tuberculate and complex. This Eiver Horse, or Sea Cow, is a very heavy and sluggish animal, attaining a length of more than eleven feet ; it resides by preference in rivers, and sometimes in the sea, and lives solely on plants, especially grasses. The Hippopotamus, which was formerly met with in Egypt, is not now found farther north than Abyssinia, but further south throughout the whole of Africa. Its stomach, though not multiple, contains three divisions, and it has an intestinal canal twelve times the length of the body, not fur- nished with a caecum. The feet, with its four short-hoofed toes, and broad palm, are admirably adapted to the habits of the ani- mal, which delights in wading about in the soft mud of shallow lakes and rivers, where it spends the greater part of the day. (3.) Odd-toed Ungulates. Dorsolumbar vertebra more than nine- teen in number; horns, when any, never in pairs. It is to be ob- 232 ELEMENTS OF NATURAL HISTORY. served that in counting the number of digits, in the odd- toed Ungulates, we are to be guided by the toes of the hind feet only. Thus, the Tapir has three toes only on the hind feet, and, therefore, is always classed with the three-toed ungulates, although it never fails to have four fingers on the fore feet. The odd-toed ungulates are divided into 1 . Solidungulates ; one-toed ; example, the Horse. 2. Multungulates ; three-toed ; example, the Tapir and Rhinoceros. 3. Proboscidians ; five-toed ; with proboscis and tusks from one or both jaws ; example, the Elephant. \. The Solidungulates are represented by the Horse and Ass, which possess feet with a single perfect toe, covered by a broad hoof, without supplementary hoofs ; incisors in a continuous series in both jaws; molar teeth complex ; two inguinal teats. Dental formula 3-3 , * ~ * .6-6 I. = -; C. - - or none; M. - > 3~3 i - i 6-6 All the species of horse belong to the Old "World, and are at home on the wide mountain plains of Asia and Africa ; they live together in troops, are very swift, and feed chiefly on grasses ; their intestinal canal is wide and long; they have a simple stomach, a large ca3cum, and no gall bladder. The domestic Horse, like the Camel, is no longer met with in its wild state, but has returned to that condition in the steppes of Asia, and in the plains of South America. The horse lives about thirty years, but sometimes over forty years ; they carry their young eleven months, and contain many varieties more or less prized and cultivated by man. The Ass differs from the horse by having his tail hairy at the end only, while that of the horse is hairy throughout ; he has also a black cross upon his shoulders, and long ears. The wild ass lives in large troops in Tartary, and migrates in winter to more southern regions. THE ODD-TOED PACHYDERMS. 233 There are three striped horses found in South Africa, which are regarded as being more closely related to the ass than to the horse ; these are, the Zebra, the Quagga, and the Onagga. The Zebra, very like the ass in build, is unlike him in dispo- sition, being the most intractable of all the solidungulates ; his skin is beautifully soft, and marked with brown and yellow stripes, which in the female become black and white. The Quagga resembles the horse more than the ass ; it is brown with black stripes, the belly and legs white ; they are very shy, and live together in troops of eighty to a hundred; they are called khona khona by the Hottentots. The Onagga, or mountain horse, is smaller than the Ass, and is striped black and white like the Zebra, with white legs. 2. The Multungulates have three toes on the hind feet, and generally three fingers, but sometimes four; the lumbodorsal vertebrae are never fewer than twenty-two ; the femur possesses a third trochanter, and the middle toe is large and symmetrical. If the species be horned, the horn (one or two) is placed in' the middle line of the head ; the stomach is simple, and the caecum large and sacculated. The Rhinoceros is so called, from having one or two horns upon its nose in the middle line ; these h,orns are formed altogether of compacted tubes, without any bony core ; it has three toes on all the feet. They are heavy animals, with a long head and short tail ; they frequent marshy places, and live on herbs and branches of trees. The villi of the small intestine are very large ; and the intestinal canal is eight times the length of the body ; the large intestine forms several large sacks at its commencement. The Asiatic species of rhinoceros have incisor teeth in both jaws, while the African rhinoceros has the incisor teeth of the lower jaw small and latent, and those of the upper jaw are either none, or disappear early. The African rhinoceros is dangerous to travellers by night, and enjoys a very acute sense of hearing and 234 ELEMENTS OF NATURAL HISTORY. of smell. The rhinoceros possesses a distinct muscle attached to the third trochanter. The Tapirs have four fingers and three toes ; the nose is pro- duced into a small moveable proboscis ; the American species are found in South America, chiefly in the neighbourhood of the east coast, in woods and moist places on the banks of rivers ; and some of them attain a length of six feet. The Asiatic species are con- fined to the peninsula of Malacca, and the island of Sumatra. The fossil animals of the Parisian Tertiary beds described by Cuvier under the name of Palceotherium, had three toes on all the feet, and were closely related to the Tapirs. The fossils described by him as Anoplotherium, were more nearly related to the Pigs, and were two-toed Ungulates. The Tapirus giganteus of Cuvier, more recently called Dinotherium, had molars resembling the Tapir, with two large tusks in the lower jaw directed down- wards ; it is now believed to have been a Marsupial mammal. 3. The Proboscidians are represented by the Elephant, of which there are only two species living. They have two incisor teeth in the upper jaw, exsert, large ; no canines ; molars large, with crown elongate ; five fingers, and the same number of toes ; nose elongated into a long prehensile proboscis ; two pectoral teats. The fossil Mastodons belonged to the Proboscidians, and are distinguished from the Elephant by the crowns of their molars having nipple-shaped tubercles arranged in pairs. The Elephant lives in forests, in the tropical regions of Asia and Africa, mostly in troops ; few of them exceed ten feet in height ; they live to a great age upwards of 100 years ; their ges- tation lasts twenty or twenty-one months, and the young elephant sucks with the mouth and not with the trunk ; they are very docile, and seem to have been educated by the ancients more per- fectly than in modern times. The Indian elephant has an oblong head, a concave forehead, ears of middling size, and four nails on the hind feet ; the bands of enamel in the molar teeth are narrow, parallel, and sinuous ; it is found native in India and Ceylon, but THE RODENTS. 2 35 not in Java. There is a variety of the Indian elephant found in Sumatra and Borneo, in which the plates of enamel are thicker and less numerous than in the Indian species ; it has also twenty pair of rihs instead of nineteen pair. The African elephant has a round head, a convex forehead, large flattened ears with semicircular flaps, and only three nails on his hind feet ; it has rhomboidal bands of enamel ; it is fiercer* than the Indian elephant, its tusks are longer, and the female possesses them as well as the male. G. THE EODENTS. Incisor teeth in both jaws, two, large, in- curved, destitute of roots ; canines none ; molars remote from incisors by an interval; mostly few, rarely exceeding four in each side of both jaws. Feet unguiculate, mostly pentadactylous. Placenta deciduate, discoidal. Fig. 130. * The revengeful ferocity, characteristic of the African Elephants, is said to have been used by the soldiers of Hannibal as a means of inducing them to cross the Rhone. " Elephantorum trajiciendorum varia consilia fuisse credo : certe variata memoria actse rei. Quidam, congregatis ad ripam elephantis, tradunt, ferocissimum ex iis irritatum ab rectore suo, quum refugientem in aquam nantem sequeretur traxisse gregem, ut quemque timentem altitudinem destituerat vadum, impetu ipso fluminis in alteram ripam rapiente." Liv. xxi. 28. 236 ELEMENTS OF NATURAL HTSTORY. The Rodents are well represented by the Squirrel, shown in Fig. 130. The incisor teeth are covered by a plate of enamel, on the anterior surface only, which in many species is coloured yellow or ruddy brown ; not only the enamel, but the anterior portion of the dentine, is harder than the back part of the teeth ; hence a greater wearing down of these teeth is e&j^ed at the back part by use, and their crowns acquire a chisel smfpe, with a surface declining from the sharp front margin backward ; the condyles of the jaws are longitudinal and not transverse, as in the Carnivores, and allow of the motion of the lower jaw backwards and for- wards. The Rodents live principally on vegetable food, often on the hard parts of plants, as bark of trees, roots, &c. They are commonly small, and exceedingly prolific ; and the species are very numerous. The Hares and Rabbits form a good example of the family of Rodents. They are distinguished from all other rodents by two small upper incisors placed behind the ordinary pair ; and they present peculiarities that approximate them, in their mode of mas- tication, to the ruminants. When the mouth is closed, the in- ferior molars lie within the margin of the superior molars, as in the ruminants, and therefore, in chewing, a large lateral motion is required, which gives to the mouth the appearance of " chew- ing the cud," as in the ruminants. The Porcupines belong to the rodents ; their body is covered with rigid, pointed spines, as is well known ; fingers four, toes generally five, but the hand is also provided with a very small thumb, resembling a wart. They are found in both hemispheres, and, with the exception of a single species, in warm countries ; they possess clavicles attached to the sternum, but not to the sca- pula ; and feed on young shoots of trees, bark, and fruits. The Beavers are aquatic rodents, having the toes of the hind foot joined by membrane, and the second toe provided with two oblique claws ; the tail is depressed and scaly. They attain HA TS AND SQ UIEREL S. 237 a length of three feet, without the tail, and live solitary in Europe and North of Asia, but form colonies in the rivers of North Ame- rica ; the social beavers are able to fell large trunks of trees by means of their powerful incisors, and so form dams across the streams on which they build their nests or domes. One-third of the known mammals are Rodents, and of the known Rodents, one half are Rats and Mice. These well known types have four fingers and a wart-like thumb, and five toes ; with distinct clavicles, and long tail. Of the house rat, there are se- veral well known varieties. The Black rat has a tail the same length as the body, and a bright glossy fur ; the white rat is a sub-variety of this kind. The Norway rat is brownish grey, and has a tail shorter than the body. This variety, which is now the common house rat of these countries, first penetrated from the East in the middle of the eighteenth century, and has ex- pelled the black rat by its superior fecundity, and not by its strength or courage, although it is larger than the black rat.* The largest known Rat is that of Bengal and Coromandel, which attains a length of two feet. Of the Rodents, altogether, there are about 700 species known, and of these, upwards of 300 are Rats ; of the remaining rodents, nearly one-half, or more than 150, are Squirrels. These well- known animals live in trees, and feed chiefly on nuts, small birds' eggs, and beetles, and they hibernate in cold weather more or less, and frequently in colder countries become white in winter. Some of them, called flying squirrels, have on each side of the body a prolongation of the skin extending between the fore and hind limbs, like the flying cats (allied to Monkeys) of Madagascar, which forms a sort of parachute, by the aid of which these ani- mals can take long leaps downwards ; these are found in Poland, Russia, and North America. * I have several times tried the Black and Norway rat in single combat, and always with the result, that the Black rat killed quickly the Norway rat, and then ate his brains. 23 8 ELEMENTS OF NATURAL HISTORY. H. THE MUTILATES OR CETACEANS. Anterior limb changed into fins ; posterior limbs wanting ; tail horizontal, flat, continuous with trunk ; no external ears. Placenta indeciduate, diffuse. The Cetaceans or Whales are divided into two groups, the carnivorous cetaceans, and the herbivorous cetaceans ; and are well illustrated by the common Porpoise, drawn in Fig. 131. K. H.jun. Fig. 131. (a). The Carnivorous Cetaceans have blowholes on the top of the head leading into the nostrils ; teats inguinal ; teeth conical, never molars with flat crowns ; body destitute of hair. The Carnivorous or true Cetaceans live almost all in the sea ex- clusively, and the largest animals in nature are found among them ; they are provided, like the pinnigrade Carni- vores, with a thick layer of fat under the skin, to protect them from the cold water. It is a mistake to suppose that these animals spout water from their blowholes ; they com- mence to expire air before reaching the surface, in order to be ready to inspire it again with as little delay as possible above the water ; the central column of air may be seen in the spout, surrounded by a clear tube of water drawn up with it by friction, and this appearance has led to the mistake that these animals spout water. The Whalebone whale is so called from its having trans- THE CETACEANS. 2 39 verse horny plates adherent to the upper jaw in place of teeth ; these plates constitute the whalebone of commerce, and are used as filters by the whale to separate from the sea water, the small sea jellies and mollusks that constitute its chief food. In some of these whales the head is very large sometimes one-third of the whole length. They have two blowholes. The Greenland, or common whale, attains a length of sixty feet, and has more than 300 plates of whale- bone on each side of the mouth. The Rorquals are distin- guished from the other whales, by having a fin upon the back, and although larger occasionally than the Greenland whale, are comparatively useless, for their whalebone is worthless, and they have much less blubber than the common whale ; some of the Rorquals have been found 100 feet in length. The Spermaceti whale is distinguished from the Greenland whale by its single blowhole, by its lower jaw furnished with a row of large conical teeth, and by its upper jaw containing a few teeth concealed under the gums. It attains nearly the size of the Greenland whale, and is met with in various seas. The spermaceti consists of a fatty substance contained in special cavities of the head, at the upper part of the skull ; and in the intestines is found the grey amber, a sort of cholesterine, which is used as a perfume, since, when burnt, it emits an agreeable smell ; this ambra grisea is some- times found drifting on the sea in warm countries, and is thrown up on the coasts. The sperm whales live upon cephalopods, and are hunted chiefly in the North Pacific, between the Sandwich Islands and Behring's Strait. The Narwhal, or sea unicorn, has two horizontal canine teeth in the upper jaw, that of the left side being, in the male, very long, straight, awl-shaped, and spirally grooved, while that of the right side is undeveloped. It often attains a length of thirteen feet, independent of the tusk, which may be ten feet more. The Dolphins and Porpoises have conical 240 ELEMENTS OF NATURAL HISTORY. vertical teeth, numerous in both jaws, and some of them attain a length of twenty-eight feet, but most of them do not exceed ten feet ; they are found in all seas, and will ascend rivers in brackish water ; they are very voracious, and swim with great speed. (#.) The Herbivorous Cetaceans. Nostrils opening in the upper lip at the anterior part of the head ; molar teeth with fiat crowns, or a horny plate instead of teeth in both jaws ; teats pectoral. These cetaceans were formerly placed in the neighbourhood of the seals, and one of them, the Manatee, was even classed in the same genus with the Walrus. They are, however, true Mutilates, and not pinnigrade, for they are entirely destitute of hind limbs. The intestinal canal is very long sometimes twenty times the length of the body as in Steller's Sea Cow ; the stomach has two blind appen- dages at its pyloric end, which is separated from the cardiac end by a constriction, and the cardiac portion of the stomach is itself a blind sack, lined with many follicles. Although the hind limbs are wanting, there are always present traces of the pelvic arch. They feed upon seaweeds, and keep near the shore and mouths of rivers. There are three kinds of Herbivorous Cetaceans known. 1 . Steller's Sea Cow. This remarkable animal formerly lived on the coast of Kamschatka, at Behring's Island, and attained a length of twenty-four feet ; it was discovered and described by Steller in Behring's second voyage. This animal has not been seen since 1768, and at the time of its discovery at Behring's Island had already become very scarce, 2. The Dugong of the Malays occurs in the Indian Ocean and in the Red Sea ; it sometimes attains a length of twenty feet. 3. The Manatees inhabit the warm regions of the Atlantic, on the west coast of Africa, and east coast of South America, fre- quenting the mouths of the great rivers of these countries. Like the Dugong, they are used as food, and considered very palatable ; THE EDENTATES, 241 they attain a length of more than fifteen feet. These are the animals that have given rise to the fables of the Mermaid ; from their pectoral mammae, and habit of holding the young between their hand-like flippers; their face is not so human as those of the seal and walrus, but is sufficiently so to apologise for the tales of the Arabian sailors. I. THE EDENTATES. Incisor and canine teeth almost always wanting, and sometimes the molars also ; toes provided with large curved, compressed claws ; sacrum formed of few vertebra ; teeth, when present, without enamel, growing as they are worn down. Fig. 132. I have selected, to illustrate the Edentates, a pair of Arma- dilloes, engaged in the congenial occupation of searching a grave (Fig. 132). All the species of this remarkable and undeveloped Order live in the warmest countries of the earth ; no animal be- longing to it is found in Europe. The Edentates are divided into two distinct sub-orders viz. the burrowing. Edentates, and the tardigrade Edentates. (a.) The burrowing Edentates have the head produced to form a long narrow snout ; the feet are short, the hinder being the 242 ELEMENTS OF NATURAL HISTORY. longer ; claws carved and adapted to digging in the ground. These animals feed upon insects, some exclusively, while others feed upon offal in addition ; a few of them climb trees, in which they are assisted by a prehensile tail ; most of them, however, live upon the ground, or under ground in holes that they have dug. These animals are represented in the Old "World by the Scaly Anteater (Manis), of Guinea and Ceylon ; and by the Anteaters of South America, especially of Brazil and Guiana. These creatures live in the forests and feed on ants, whose nests they tear up with their large nails ; they possess an extensile tongue, covered with an adhesive mucus, which is used for the purpose of licking up their food. Some of them are four feet long, exclusive of their bushy tail, which is often two and a half feet in length. In South Africa there is a species of burrowing Edentate, called the ground Hog ( Orycteropus], which lives in subterranean cavities, and attains a length of upwards of four feet. The Armadilloes of South America are distinguished by the peculiar breadth of the first rib, by well-developed clavicles, by a projecting line parallel to the spine of the scapula, and by an elon- gation of the acromion beyond the head of the humerus. These are all characters, showing the extent and power of the muscles employed in digging ; they can bury themselves in the ground when pursued, and tunnel through it as fast as a man can follow them with a spade. (b.) The Tardigrade Edentates have the head truncated anteriorly ; the legs, especially the fore legs, very long ; and the claws compressed and incurved. These animals, popularly called Sloths, live in South America, in the forests, and feed upon the leaves of trees, from which they hang suspended by their curved claws. The Edentates are especially remarkable for the gigantic species belonging to this family that lived in South America before the creation of man ; among the most THE MARSUPIALS. 243 remarkable of which may be named, the Megatherium, a fos- sil Sloth that exceeded the Rhinoceros in bulk ; and the Glyptodon, a fossil Armadillo, upwards of nine feet in length. The non-placental Mammals are divided into two great groups, which probably differ as much from each other as they both do from the placental Mammals. These divisions are II. Non- 'Placental Mammals. K. Didelphs or Marsupials. L. Ornithodelphs or Monotremes. K. DIDELPHS OR MAUSUPIALS. These animals were so named by Linnaeus, because they are provided with an abdominal bag (marsupium), in which the immature young are placed by the mother after their birth, and this bag performs the part of a second womb (6te\0v norms. F. Scolecids. j A. Insects. This class of Articulates has the head distinct from the trunk, with sensitive antenna? ; their respiration is performed by means of air canals distributed internally through the body, and divided into very fine branches. The first of these two characters distinguishes the Insects from the Arachnids, in which the head and thorax form a single piece, and which have non-sensitive antenn* ; and the second distinguishes them from the Crustaceans, which possess gills, or other external ap- pendages intended for breathing water. The Insects resemble the Myriapods in many particulars, but are distinguished from them by the lesser number of their ring segments, which in In- sects never exceed twenty, while in the Myriapods they are always greater than that number. Five or six of the ring segments are combined, in Insects, to form the head ; three or more of the seg- ments are combined to form the thorax, to which three pairs of locomotive limbs, characteristic of perfect insects, are attached. Two additional pairs of locomotive organs (wings) are developed from the dorsal surfaces of the second and third thoracic seg- ments, in most Insects. The antenna of insects are supposed by some to be the organs of smell, others believe them to be the organs of touch, and it has been asserted that they are the organs of hearing ; they are un- connected with the mouth and are placed near the eyes, and they 296 ELEMENTS OF NATURAL HJSTORY. derive their nerve filaments, like the eyes, from the anterior, or cerebral ganglion of the double nerve cord. The eyes of insects are either simple or compound ; the simple eyes being named eyepoints, and are like smooth shining points placed usually in a triangle behind the compound eyes, as in Bees and Wasps. The larger, or compound eyes, are formed by a large number of eye tubes, closely pressed together, so that each of them has become hexagonal ; these are arranged on the sides of the head, on large convex surfaces which frequently, as in the Dragonfly, occupy the greater part of the head. These facetted eyes have been frequently counted, and are often found to exceed 8000 in number, as in the Fly and Cockchafer. The mouth, of insects consists of six pieces ; two placed ver- tically, at top and bottom, called the upper lip (labrum) and lower lip (labium} ; and two pairs placed horizontally, one above the other, opening and shutting horizontally, which are called jaws, the upper pair of jaws being named mandibles, and the lower pair, maxillas ; the lower jaws are generally employed to hold the food while it is masticated by the upper pair. The heart of insects has the form of a long pulsating arterial vessel terminating behind in a blind extremity, and lying above the intestines on the dorsal surface of the body : the hinder end of the heart is surrounded by a cavity containing venous blood, which may be regarded as performing the part of an auricle, and the blood is admitted into the heart by eight or nine pairs of lateral openings, closed with valves, which allow of the entrance of blood, but prevent its exit. The blood received into the heart through these lateral openings is pumped forwards by its pulse- like contraction, and distributed backwards through the body, following the track of the air canals. The air canals of insects resemble the spiral vessels already described in plants, for they possess, between their outer and inner coats, a flat horny elastic thread coiled up spirally, which has the effect of keeping the canal always open. These canals INSECTS. 297 open externally on both sides of the thoracic and abdominal rings, by narrow slits called stigmata, but rarely by more than nine* pairs of such openings. The air canals divide and subdivide into smaller and smaller branches through all parts of the body of the insect, and are followed in their course by the ramifications of the arterial vessels, so that the blood of insects is oxidized, not in special organs, as lungs or gills, but in every part of the entire body. Many of the insects also that live in water really breathe by means of air taken from the water into their air canals, while their larvae breathe the air in the water by means of gills ; these latter have no stigmata or air slits. Many insects undergo a three-fold transformation, in their growth from the egg to the perfect insect. On leaving the egg, the insect is called a larva, or caterpillar ; it resembles a worm, has numerous pairs of legs, eats voraciously, grows rapidly, and often casts its skin, acquiring a new and larger skin to suit its rapid growth. After casting the skin for the last time, the ani- mal assumes quite another shape, having a hard horny skin ; it has no limbs, takes no food, and seems wrapt in a profound slumber; in this condition it is called a pupa. Important che- mical and physiological changes, however, take place during the time (often many months) for which the insect exists in its pupa form; the stores of fat accumulated by the voracious larva gradually become absorbed and disappear ; and the organs proper to the perfect insect are slowly elaborated. At last the perfect animal bursts its narrow cell, and emerges into day, when it is called the imago. At first the wings are short, moist, and unfit for flying, but they are soon unfolded and dried, and support in the air the full-grown insect, which fulfils the remaining duty of its short life the propagation of its kind and then dies. * In the Mole cricket there are ten pairs, three in the thorax, and seven in the abdomen. 29 8 ELEMENTS OF NATURAL HISTORY. The following Orders of the class of insects are recognised by Naturalists : a. Apters Wingless. b. Strepsipters "Wings twisted. c. Dipters Two-winged. d. Hymenopters Wings membranous. e. Lepidopters Scales on wings. f. Neuropters Wings with strong netted veins. g. Hemiptcrs Half-winged. h. Orthopters Straight-winged. t. Coleopters Wings furnished with sheaths. (a). Apters. The wingless insects include three sub-orders, viz., r . Thysanours Fringed tails. 2. Parasites Parasites. 3. Suetorians Suckers. The Thysanourans are minute insects, with six feet, and with- out wings, not undergoing metamorphosis, not parasitic, eyes sim- ple, in two groups ; they are furnished with bristles at the end of their tail, which fold under the insect when at rest, and by their sudden straightening, the animal is thrown forward with a leap. Hence they are sometimes called Springtails. These insects pre- sent many analogies with the Myriapods, and the Orthopters, especially the Earwigs. The sub-order includes the Sugar Lice and the Springtails. The Sugar Lice were originally imported in sugar from America into Europe ; with us they now generally live in books on damp shelves ; they run rapidly and are covered with small silvery scales, which are used as tests for micro- scopes. The Parasites are better known than loved ; they have six feet, no wings, are parasitic, and do not undergo metamorphosis ; eyes one pair, simple, or none. The Parasites include the Lice. The body ..of Parasites is flattened, semi-transparent, and contains eleven or twelve distinct segments; the stigmata of the air WJNGLESS INSECTS. 299 canals are very large, and are shown in Fig. 163, which repre- sents a view of the human louse under the microscope ; the antennae are short and com- posed of five segments ; the legs are short and furnished with stout claws, by means of which these animals cling to the hairs of ani- mals, or feathers of birds, whose blood they suck, and on whose body they propagate and pass their lives. Almost every mammal and bird is infested by one or more parasite in- sects, upwards of 500 varieties of which, mo- Fig. 163. delled on the disgusting pattern of the human louse, Fig. 163, have been figured and described. Man himself enjoys the pri- vilege of possessing three such humble companions, named respec- tively by naturalists Pediculus corporis humanus The Clothes Louse. Pediculm capitis humanus The Head Louse. Phthirus pubis The Crab Louse. The fecundity of these brutes is fearful, and under specially favourable, but unknown conditions of the blood of their victim, their developement becomes so excessive, that they seem, as it were, to pour from the body, and may be regarded as a symptom of serious disease. The term morbus pediculosus has been given to this terrible malady. The Suctorians are better known by the name of Fleas. They are wingless, with six feet, and undergo perfect metamorphosis; mouth suctorial, having each maxilla furnished with two feelers stretching forward. The Suctorians are distinguished from the sucking Hemipters {Bugs), by their perfect metamorphosis, and by the presence of palps on the maxilla. In fleas there may be seen four minute scales, on the last two segments of the thorax, which are regarded as rudimentary wings. Different kinds of fleas infest different animals, whose blood they suck ; and it is 300 ELEMENTS OF NATURAL HISTORY. said that although the dog flea will hite man, and the human flea will bite the dog, the change of diet disagrees with them, and they shortly die. The human flea (pulex irritant) lays about a dozen eggs in summer, in chinks of wooden floors, or furniture ; these eggs are white, oblong, and sticky, and give birth to thin, wiry, active larva?, after a lapse of six days ; these little worms wriggle about like serpents, and roll themselves into flat spirals like that of Archimedes. They are provided by the foresight of their mother (herself taught by " Him who feeds the sparrows") with a nutritious and suitable food. Having selected suitable subjects among her human friends, she sucks their blood, and car- ries it to the place where she has laid her eggs ; it is then dis- gorged from her gullet, and dries into a black globule, many of which are placed by the parent flea in the vicinity of her eggs ; and these globules of human blood are observed to form the fa- vourite food of the active little larva. After eleven days spent in the enjoyment of preserved blood, the larva? having attained their full growth, spin themselves up, and change into pupas, from which again, after ten or eleven days, the perfect imago emerges, both willing and able to change his diet of dried blood into the fresh- drawn blood of his human victims. Having once tasted this nec- tar, nothing will induce the flea to give up its pursuit ; neither threats nor remonstrances are availing, and many millions of these little animals perish annually in their unequal contest with man. Their lively movements, however, and active disposition, win them the respect of their destroyer, who prefers their troublesome attacks, to the society of the hateful louse, and al- ways gives them the boon of the Cyclops to Ulysses that he will destroy them last. OVTIV lyia -rrvfiarov iSofiai fitra olf irapoioiv, TO 5i TOI ,nvr{iov IOTO.I. (I). Strepsipters. These little insects, like those last described, are parasitic, and infest the Bees, and others of the Hymen- TWO-WINGED INSECTS. 301 opterous Order ; they differ so much in structure from other insects, that they are placed in a separate order, the charac- ters of which are as follows : Small insects with six feet; male furnished with four wings, of which the first pair are rudimentary only, and the second pair are large, membranous, and shaped like a quadrant of a circle, and are folded when at rest longitudinally like a fan; female without either feet or wings; metamorphosis complete. Larva and pupae living parasitically in different kinds of Hymenopters. The males have compound eyes. These minute insects, in their con- dition of larvge and pupa?, were long known to infest the bee as parasites ; but we owe the complete investigation of their metamorphosis, and of the differences of the sexes, to the observations of the Rev. Mr. Kirby. A magnified view of the adult male is given in Fig. 164, which shows well the de- velopement of the posterior pair of wings, and the compound fa- cetted eyes of the bee-parasite called Stylops. Fi S- l6 4- (c.) Dipters, These insects, like the last, have only two wings, but it is the anterior pair of wings that is developed, the posterior pair being rudimentary, and consisting each of a thin pedicle, with a button at top; these are called poisers; they have six feet, and a suctorial mouth, formed of the labium produced into a proboscis ; their metamorphosis is complete ; their larva? are generally long lived, and have no feet; some of these larvae, in passing into pupa?, do not change their skin, but the latter shrinks, hardens, and forms a pupa case, from which the larva separates and undergoes its transformation. Many of the Dipters attack man, and the domesticated animals, and suck their blood ; others injure him by depositing their eggs on flesh and cheese, in which 302 ELEMENTS OF NATURAL HISTORY. their larvae are developed, and on which they feed. They include the Gnats, Horse Flies, Flesh Flies, the Tsetse, and many others. The common House Fly (Fig. 165) will serve as a representative of the en- tire order. The larva? of the common house fly live especially in horse dung, and are found only in the neighbourhood of human habitations ; the larva is full grown in four- teen days, and in fourteen days more the Fig. 165. pupa produces the full-grown fly, while the egg requires only a single day (if the weather be warm) to produce the young maggot. Thus it happens that a whole generation of house flies may succeed another in a month's time ; and in the meanwhile, the old stock of flies has not died off, for they live on until the frosts of early winter. Hence it is that the sudden increase of flies at the beginning of the autumn that follows a warm summer is readily explained. The re- production of the Flesh fly (Musca carnaria) is still more rapid, and it has been estimated that the progeny of a single female of this species during one summer may amount to 500,000,000 of new flies. Naturalists have, in various ways, expressed their just astonishment at the power of destruction of carrion implied in such a wonderful fecundity; thus Linnteus says, " that three flies could consume the body of a horse as quickly as a lion could;" and Meigen says, " that if Nature had not provided powerful counterplots for their destruction, these gentry would soon leave to Man so little flesh to eat, that fast days would become the fashion." (d.) Hymenopters. Insects with six feet, and four membranous wings ; the second pair smaller, and having feicer veins; max- illa long, encasing the upper lip ; tail of females almost always furnished with a sting ; metamorphosis complete. This order of insects is distinguished by the possession of four mem- branous wings ; it is separated from the Neuropters by its HYMENOPTERS. 303 wings possessing simple veins, and the second pair being smaller than the first pair ; whereas, in the Neuropters, the veins are netted. Their nearest neighbours are the Dipters, and Aristotle first pointed out the distinction between the Hymenopters and the Dipters, by stating, that the Hymen- opters have a sting in their tail, whereas the Dipters have a sting in their head, and the Coleopters have no sting at all. The Dipters, in fact, wound in order to feed, and the Hy- menopters' wound to defend or avenge themselves. The Hymenopters include the Gall Flies, Ants, Wasps, Bees, and many other families ; some of which are remarkable for their intelligence and instinct. The first, or cephalic ganglion, in these insects is unusually large, and the optic nerves are greatly developed ; they possess, in addition to a pair of large compound facetted eyes, three pairs of simple eyes. Many of these insects live together in families, and develope social in- stincts that have attracted the notice of observers from the earliest times. We shall select as the best known example of the Hymenopters, the common Honey Bee. In England alone, upwards of 250 species of Bees have been described, all of which, including the Honey Bee, are originally natives of Asia and Europe ; and some of them, including theHoneyBee, have been introduced by man intoAmerica. The Honey Bees are social, each hive containing from 15,000 to 2 0,000 individuals, of which 600 to 800 are Drones (males), one is the Queen (female), and all the others are Workers (neutral fe- males). The relative sizes and forms of these three kinds of bees are shown in Fig. 1 66, in which a represents the Drone, b the Work- ing Bee, and c the Queen. It is one of the disadvantages attend- ing civilised society, that a division of labour not known in savage life becomes necessary, and this division of labour takes different forms in different kinds of society. Satirists have availed themselves of the arrangements arising from social combinations to draw comparisons between men and bees, not always to the ad- 34 ELEMENTS OF NATURAL HISTORY. vantage of the former ; thus, the neutral workers are compared to our old maids, the power of the former residing in their tails, Fig. 1 66. that of the latter in their tongues ; and the zeal of the work- ing bees in providing food and lodging for the progeny of their more fortunate sister, the Queen, is contrasted with the grudging services rendered by our old maids to the children of their married sisters. Again, the bees put all the Drones to death as soon as they have fulfilled their duty, and are no longer useful ; we, on the other hand, make Field Marshals of our Drones, and allow them to interfere in the affairs of State. It has been ascertained that the Working bees are nothing else than imperfectly developed females, and that if the larvae (which would naturally produce workers), be removed within three days after leaving the egg, to the larger royal cells, and there receive a more abundant and fluid nutriment, they will grow into fruitful bees, or Queens, instead of common working bees. The instincts, therefore, of the "Workers are the instincts of females; the stronger of them go abroad in search of food, which they find in the nectaries of plants ; and part of this honey food they convert into wax to form material for their cells, and part they store up in the cells that they have made ; in the mean time, the weaker BEES. 305 of the working bees remain in the hive, look after the feeding of the larvae, and attend to other domestic duties. 'Hire tQvta flat fitXifftrdwv ddivdwv, Ilsrpj/e IK y\av BorpvSov Si TTfTovTai ITT' avOtatv liapwoioiv At fiv T' tv9a a\iQ irtTrorjjarat, at le n tvOa. ILIAD. " Qualis apes aestate nova per florea rura Exercet sub sole labor, quum gentia adultos Educunt fetus, aut quum liquentia mella Stipant et dulci distendunt nectare cellas, Aut onera accipiunt venientum, aut agmine facto Ignavum, fucos, pecus a praesepibus arcent ; Fervet opus redolentque thymo fragrantia mella." " For so work the honey Bees ; Creatures, that by a rule in nature teach The art of order to a peopled kingdom. They have a King, and officers of state ; Where some, like magistrates, correct at home ; Others, like merchants, venture trade abroad ; Others, like soldiers, armed in their stings, Make boot upon the summer's velvet buds, Which pillage they with merry march bring home To the tent royal of their Emperor, Who busied in his majesty, surveys The singing mason building roofs of gold ; The civil citizens kneading up the honey ; The poor mechanic porters crowding in Their heavy burdens at his narrow gate, The sad-eyed Justice with his surly hum, Delivering o'er to executors pale The lazy yawning Drone." HBNRY V. The larvae are hatched in three days, and five days afterwards they prepare to change, surrounding themselves with a fine web, on which they expend the labour of a day and a-half; in three x 3 ELEMENTS OF NATURAL HISTORY. days they are converted into pupae ; the imago or perfect insect is produced from the pupa in eight days. The foregoing are the ordinary changes of the working bees; those of the Queens occupy a shorter time, and those of the Drones somewhat longer. Many of the Wasps and Ants are social in their habits, like Bees, but their societies are more democratic. It may be worth while to describe briefly the political state of the three communi- ties. Among the Bees, one Queen only is recognised in the hive, and she is treated with the greatest attention by all the working Bees, each of whom visits her from time to time and satisfies her- self of the Queen's presence in the hive, apparently by smelling her with the antennae ; if the workers be prevented occasionally examining the Queen with their antennae, they take for granted that she is lost, and immediately proceed to manufacture a new Queen, as I have already described. If the Queen be removed from a hive, and a strange Queen introduced at once, she is sur- rounded by workers and kept a close prisoner until she dies of hunger ; for the workers will never sting a Queen. If, however, some twenty hours have elapsed since the removal of their own Queen, the workers, instead of starving her to death, adopt her as their own, and admit her at once to the sovereignty of the hive, as if glad to escape the trouble of making a new Queen, by fattening a worker larva. When, however, a new Queen is in- troduced into a hive already in possession of a Queen, or when two young Queens emerge simultaneously from the royal pupa cases ; each becomes surrounded by a crowd of workers, which prevent her escape, and the Queens are compelled to fight for the sovereignty of the hive. The workers look on with delight at the struggle for supremacy, without daring to interfere, or to aid either of the combatants ; and, so far as man can j udge the feelings of insects by his own, their emotions during the contest must resemble those of the curates of a diocese whose Bishoprick is vacant, who behold, with mingled feelings of terror and pleasure, WASPS AND ANTS. 307 the fearful struggle for the empty Mitre, between two rival Dignitaries. The Wasps are more democratic in their nature than the Bees, and yet they tolerate with composure the presence of nu- merous Queens in their society, many hundreds of these monarchs being found in a nest of wasps, at the close of summer ; the reason of this extraordinary indifference to monarchical usurpa- tion is to be found in the fact, that all the neutral or working wasps are destined to perish in the cold of winter, whereas their Queens will survive the winter and commence the battle of life in spring ; now the wasps are philosophers, and know their fate, to which they resolve to submit with resignation, and they there- fore enjoy, while they can, a jolly and roving life; they are freebooters, and attack fruits and flesh, on which they feast them- selves ; but, at the same time, as good fathers of families, mind- ful of the maxim of Voltaire, " ces peres de famille sont capables de tout !" they make it a point to attack plain working bees on their return from a hard day's work ; these they kill and rob, carrying home their honey, not for their own use, but to feed their larvse with it. The association of robbers, called a wasp's nest, owes its origin to a single mother Queen, who has survived the cold of the preceding winter ; she builds her nest in spring, and lays her eggs in it, from which are produced the neutral wasps that are her first offspring ; these furnish her with food, and help to make the new cells required by the increasing colony ; and so they rob and plunder all around them, after the established custom of republics, and towards the end of autumn, close their eyes to the dangers that threaten the commonwealth, from the increase of young Queens, consoling themselves unconsciously with the reflection of the rascally statesman " Apres moi le deluge." The Ants are as sociable in their habits as the Bees, but are less easily observed ; they are as democratic as the Wasps, but have studied political economy as well as liberty. The worker x2 3 o8 ELEMENTS OF NATURAL HISTORY. ants are undeveloped females, like the corresponding class among Bees and Wasps, but they survive the cold of winter, and there- fore, unlike the careless wasps, they have a future to look forward to and provide for : instead, therefore, of crowning a single Queen, like the Bees ; or allowing a multitude of Queens to grow up in the community, like the Wasps ; they take the most scrupulous care of the larvae and pup belonging to the republic, airing them in the sunshine, and hurrying them below on the approach of rain ; but as soon as the imago insects are prodxiced, they hasten to remove them from the nest, whether Drones or Queens ; and compel them to fly abroad in search of mates. Many of these thoughtless insects are devoured by birds, or drowned in water, and so made food for fishes ; the females, or Queens, that are left now divest themselves of their wings by means of their feet, and are ready to lay new eggs and found a new colony. The cunning workers readily recognise them by their want of wings, pounce upon any of them they can catch, and drag them to the nest, where they are compelled to lay their eggs ; when that is accom- plished, the unhappy mothers are driven by the workers, with- out mercy, from the nest, and perish miserably, being starved, secundum artem, according to the maxims of political eco- nomy. (e.) Lepidopters. Insects with six feet ; and four membranous wings, covered with minute coloured scales ; mouth with invo- lute spiral tongue, formed ly the prolonged maxilla ; metamor- phosis complete. These insects include the well known Gut- ter/lies and Moths. The scales that cover their wings seem like dust to the naked eye, but under the microscope appear arranged in regular rows, like house tiles or scales of fish. Their larvae are called caterpillars, and consist of twelve rings, exclusive of the head ; they are furnished with nine pairs of air slits, for the second, third, and last ring have no slits. They have eight pairs of feet, the fourth, fifth, tenth, and eleventh rings having no feet. Most caterpillars live on MOTHS AND BUTTERFLIES. 309 vegetable food, and many are confined to a single species of plant; others, however, especially of the Moths, eat leather, fur, fat, and wax The Lepidopters are divided into noc- turnal, crepuscular, and diurnal. The Nocturnal Lepidopters are Moths ; their wings are guarded by a part called the retinaculum, which consists of a horny elastic hair, arising on the anterior margin of the hind wings close to their insertion ; a little flat ring on the under surface of the fore- wing allows it a passage, and thus both wings are connected, and so compelled to move together as one wing during flight. Their wings when at rest repose horizontally and not vertically, as in the Butterflies. The well known Silkworm moth, intro- duced into Europe in the time of the Emperor Justinian, belongs to the sub-division of Nocturnal Lepidopters. The Crepuscular Lepidopters, called also Sphinx Moths, are Fig. 167. distinguished from the moths by the form of their antennae ; which in the nocturnal Lepidopters are shaped like hairs or bristles, tapering from the base to the point ; while in the cre- puscular Lepidopters, the antennae are club-shaped, increasing in size from the base to the point. Their pupae are never angular, like those of the Butterflies, but are generally smooth, and some- times furnished with small spines.' The Death's Head Hawk Moth (Sphinx atropos) Fig. 167 (so called from the death's head 3'0 ELEMENTS OF NA T URA L HIS TOR Y. and crossed bones marked upon his back) is one of the largest of European Lepidopters ; it measures five inches across the wings ; its larva is of a greenish yellow colour speckled with black, and measures, when fully grown, five inches in length ; it feeds upon the potato plant and the jasmine, and buries itself in the ground before becoming a pupa. It is produced in this country, in hot summers, about the beginning of October, and its appearance in large numbers is much dreaded by the country people in the South of Ireland, and in Brittany ; partly because of the ill-omened mark upon the insect's back ; partly because of its feeble croak, that resembles the squeak of a sick mouse ; but chiefly because the hot summer, that produces this Moth in abundance, has been often followed in the West of Europe by the outbreak of deadly epi- demics. The Diurnal Lepidopters, well known as -Butterflies, have the wings mostly erect when at rest, and never bridled by a retina- culum. Their caterpillars always have eight pairs of feet ; and their chrysalis is almost always naked, angular, attached poste- riorly by threads, or suspended vertically, or affixed by a trans- verse silken cord expanded above the middle of the body ; the Butterflies have club-shaped antenna, often terminated abruptly by a knob. (/) Neuropters Insects with six feet; four wings, membranous, transparent, reticulate, nearly equal ; metamorphosis frequently incomplete; larva with six feet. The veins, or nerves of the wings are reticulated, and the hind wings are usually as large as the fore wings ; they are distinguished from the Hymenopters by their females having no sting. Most of the larvae of the Neuropters are aquatic ; and many of the fully developed insects display much instinct, as the Ant lion and Termite. This order of insects includes the Caddis worm, the Dragon flies, and the May flies, the Ant lions, the Ter- mite Ants, and others. The Caddis worm and May flies are well known to the NEUROPTERS. 3 I I angler, and are usually placed among the JS"europters, al- though their wings cannot be considered as reticulated. The Cad bait is the larva of the Caddis fly, and lives in the water, in cases made artificially of bits of sticks, grains of sand, small shells, and other substances, which are held together by silken threads secreted by the worm itself; these cases serve as a pro- tection to the larva during its early life. The May flies, also called Ephemerals, because they live in the imago state only for a single day, spend years in the larva condition, in wet places or altogether under water ; the nymphs, like the larva?, live at the bottom of the water, between stones, or in the ooze ; and the change from the nymph to the imago is so sudden, that there is almost, at the same moment, a creeping and a flying insect. At the close of May, particularly on its last three days, there takes place what is called "the dance of the May flies," when these little creatures, produced to exist for twenty hours, enjoy their happy dance, and seem as difficult to count as the flakes of falling snow in winter ; this dance is performed mostly over running water, and is watched with interest by many species of fish, espe- cially the roach, which feasts itself and grows very fat on the bodies of the little dancers. Their bodies are collected in Car- niola, and in the neighbourhood of Lough Neagh in Ireland, as manure for land. The great Linnaeus has thus celebrated the history of the May flies : " Ephemerae larvae natant in aquis ; volatiles factae fruuntur gaudio, uno saepe eodemque die, nuptias, puerperia, et exse- quias celebrantes." The Dragon flie (Fig. 168), are among the most active and voracious of insects ; as larvae, as pupa?, and as flies, they are greedy and strong ; they have very large facetted compound eyes, and also three simple eyes. In the larva state they are aquatic, and engaged in unceasing war with other insects ; their pupa condition also is one of activity and is passed under water ; they are in this state furnished with a sort of mask formed out of the 3 I2 ELEMENTS OF NATURAL HISTORY. lower lip (labium) with which they cover their jaws; and they use this curious mask in order to alarm and seize their prey, Fig. 168. projecting and retracting it at will. In the imago state they are so ferocious, that they have been known to attack and devour their own bodies ! The Lion Ant and the Termite Ant are foreigners, but are well known from the descriptions of travellers. The larva of the Lion Ant is celebrated for its cunning; it has six feet, very large upper jaws (mandibles], and a flat head, with oval abdomen. This animal digs a hole in sand, of a funnel shape, the sides of the cone necessarily lying at the angle of repose, so that an incautious insect, coming to the edge, must slip down to the bottom, where the Ant lion lies buried in the sand, and immediately grips his victim with his powerful forceps, and devours him without mercy. The Termites, or White Ants, are social insects, and are even more complicated in their economy than in the social Hymenop- ters. They live principally in warm countries, where they cause infinite damage. They leave the surface of the woodwork or NEUROPTERS. 3*3 furniture attacked by them untouched, so that everything pre- serves externally its usual appearance, but falls to pieces on the slightest touch ; glass, metal, and stone alone escape their ravages. Fig. 169. In Guinea and other parts of Africa they build conical mounds, twelve feet in height ; in the centre of the mound is placed the residence of the Queen, and round the royal residence are ranged the royal cells, magazines for food, and other conveniences. The Termite Queen (Fig. 169) is the most fertile of insects, and is capable of laying 80,000 eggs at a sitting. The males have wings, and seem to be guarded by the workers as carefully as the Queen. Of the neutral, or undeveloped Termites, there are two distinct kinds, one called workers, and the other called soldiers ; the duty of the former is the same as that of working bees and wasps, while the duty of the latter is altogether defensive, and they are furnished for the efficient discharge of this duty with a pair of powerful pincer jaws. (g.) Hemipters. These are insects with six feet ; with four wings, I?5< these, nearly two inches in length, is shown in Fig. 176; it is pitchy black, with antenna? and feelers red brown. It may be distinguished from the Dyticus either by its antennse or by its habits. The antennse of the DyticidaB are longer than the head, bristle-shaped, and have eleven joints ; whereas the antenna? of the Hydrophili are short, inserted in a deep fold under the side of the head, and are terminated by a club. The Hydrophili also have only four labial feelers, while the Dy- ticid have six. The Hydrophili, moreover, breathe quite differently from the Dyticidae : when they feel the necessity for fresh air, they rise to the surface, with Fig. 176. the head upwards instead of downwards, and cover the abdomen MYRIAPODS. 323 with a stratum of air by means of the antennae ; this provision of air for breathing shines under water like silver, in consequence of the total reflexion of light from its surface. The thorax of the Hydrophili is terminated by a sharp spine, between the hind legs, which often hurts those that handle them incautiously. B. Myriapods. These articulates have respiratory organs formed of air canals like those of Insects, from which they are distinguished by having always more than twenty rings in the body ; their feet are numerous (twenty-four or more), disposed along the whole body, and each terminated by a single claw ; the head is distinct from the thorax, but there is no well-marked di- vision between the thorax and abdomen ; they must be regarded as inferior in organisation to perfect six-footed insects, but they show many resemblances to the larvae of these animals. They resemble Worms in their mode of growth, for in early life they have few rings, and only three pairs of feet ; but as they grow, new rings are formed, and the number of feet is increased. Many of the Myriapods are characterised by having two clusters of single eyes, the number of which, like that of the rings of the body, increases with their developement. The Myriapods are usually divided into two sections the Centipedes and. Millepedes so named roughly from the greater or lesser number of their feet. (a). Centipedes. These Myriapods are carnivorous, and have the second pair of feet furnished with pincers, terminated by a strong hook, which is perforate, and gives passage to a poi- sonous secretion. The body is depressed, covered above and below with horny plates, and membranous at the sides; their feet are lateral, generally a single pair to each body ring, the posterior feet being the longest and extended back- wards. These animals are very active, and can run and turn the body very quickly, so as to creep into curved pas- sages in pursuit of their insect prey. The Scolopendra (Fig. 177) is the largest and most dangerous of the Myriapods, y 2 324 ELEMENTS OF NATURAL HISTORY. often reaching in South America a length of fourteen inches, and one and a quarter inch across the body ; it has, gene- rally, twenty-one pairs of feet behind the clawed feet ; and is Fig. 177- furnished with four single eyes at each side of the head, be- hind the base of the antennae, which have from seventeen to twenty joints. The Scolopendra gig as is much dreaded in South America, where it often takes refuge in furniture and beds ; but its bite has very rarely proved fatal to man. (b.) Millepedes These Myriapods are easily known from the Centipedes, by their round worm-like body, and greater number of feet, which gives their motion a slow vermicular appearance ; also their antenna are short, and contain only six or seven joints, instead of the fourteen to forty found among the Centipedes. They are innocent little animals, and live chiefly on vegetable food, while some eat also dead earthworms and small mollusks. Many of them diffuse a disagreeable odour, caused by a greasy fluid that is excreted from a small sack placed in each body ring, and at each side. The little garden Millepede (Julus) is shown in Fig. Fig. 178. 178 ; it rolls itself up spirally with the head in the middle, and the numerous delicate little feet placed inside, so that it ARACHNIDS. 325 is comparatively protected, and in this posture it passes the winter. The eggs are deposited in spring by the female, who lays sixty or seventy in a hole prepared in the ground, and after three weeks the young make their appearance, without legs ; after a short time they acquire three pairs, and afterwards additional rings and pairs of feet are developed in the part of the body placed in front of the penultimate ring. C. Arachnids. Articulates with jointed feet ; head and chest united into a cephalothorax ; fert eight in number, not abdominal ; circulation performed by dorsal pulsating vessel ; respiration va- rious. The Arachnids include Spiders, Scorpions, Mites, and Sea Spiders. (.) Spiders. Feelers thread-like; abdomen covered with a soft skin, joined to the cephalo-thorax by a stalk; air slits two or four, opening into lungs. These well-known animals spin silky filaments, from which they prepare their webs and nets, and with which they always cover their eggs. These threads are formed by four or six spinnerets, placed at the hinder end of the body, from which the silky threads are drawn out through fine tubes. Spiders are furnished with single-fingered mandibles, having a perforate terminal claw, for the discharge of a poisonous excretion ; their feet are of different lengths, but similar in form, and each terminated by a double or triple claw. The habits of Spiders are very various, and, accordingly, they have been divided into the following groups : 1. Hunting Spiders. 2. Wandering Spiders. 3. Prowling Spiders. 4. Spinning sedentary Spiders. 5. Swimming Spiders. The hunting Spiders have the habits of Wasps, and spend 326 ELEMENTS OF NATURAL HISTORY. their time incessantly running or leaping about the vicinity of their natural abode, to chase and catch their prey. The wandering or vagabond Spiders are real tramps, and have no fixed homes; they take long journeys, without caring to re- turn, in search of food ; and only stay for any length of time in the same place when about to deposit their eggs. The prowling Spiders form threads and nets to catch their prey, but do not sit in the web they have made ; they prefer to prowl about in its neighbourhood, returning to it from time to time, like fishermen that have set long lines, which they return at intervals to examine. The sedentary spinning Spiders are those best known to the generality of observers ; they always live either in the middle or at the side of their symmetrical web, to be in readiness to attack the insects entangled in it. They are considered to resemble chamber lawyers, while the other Spiders are more like attorneys. The swimming Spiders live in water, and there form a bell- shaped waterproof web, filled with air, and open below ; this web is fastened by them to water plants by slender threads. These Spiders breathe air exclusively, and carry it about their persons, like the Hydrophilous Beetles. (i.) Scorpions. The Scorpions have large feelers (not antennae) resembling feet, with pincers; abdomen divided into segments; and breathe by four or eight pulmonary sacks. They live in warm regions of the temperate zone, and in tropical coun- tries. They possess a poison gland in the last joint of their tail, which renders their wound somewhat dangerous. Their body is composed of twenty rings, of which six are allotted to the head ; and the last five segments of the body are nar- rowed into a tail. They lurk under stones in the neighbour- hood of old buildings, and sometimes enter dwelling-houses; they run about quickly, brandishing their tails over their backs, and are thus more readily seen and avoided than the Scolopendrte. CRUSTACEANS. 327 (c.) Mites, or Acari; have the cephalothorax united with the ab- domen, ichich is not divided into segments ; mandibles forceps- shaped; eyes none; feet terminated by an adhesive cup and by a claw. These are well-known little animals, many of them being parasitic ; they all breathe, like insects, by means of air canals ; and many of them live in cheese and other provisions, in which situation they multiply exceedingly. A species of Mite that digs into the flesh of Scotchmen is called the Sarcoptes Scabiei, and produces the "Itch" ; other varieties are connected with the rare disease called "plica Polonica," which is now becoming fashionable in Western Europe since the introduction of " Chignons." Similar ani- mals are found in the horse and in mangy dogs. (d.} Sea Spiders. These, as their name implies, are wholly marine, and on this account were long supposed to be Crus- taceans. They have no organs of respiration. Like the true spiders, they are provided with eight legs, which in some species attain an extraordinary length, and include caecal prolongations of the stomach. D. Crustaceans. The Crustaceans are articulate animals, without wings; having jointed feet, both thoracic and abdomi- nal ; breathing mostly by gills, but some- times by the skin, without air slits ; heart often distinct, aortic, and dorsal. The circulation of blood in the higher Crustaceans is effected, as in the higher Mollusks, by means of an arterial heart, and not, as in the Fishes (Fig. 152), by a venous heart. The heart is dorsal, and gives off arteries to the eyes and antenna, to the liver, and to the intestines and ge- nital organs ; the blood, distributed to these various organs, re- turns through the gills to the heart, having become oxidised in Fig. 179. 328 CLEMENTS OF NATURAL HISTORY. those organs (Fig. 179); whereas in Fishes (Fig. 152) it is first distributed to the gills, and thence forwarded to the various parts of the body. The Crustaceans are divided into the following Orders, ex- clusive of some that are only found Fossil : a. Podophthalms, or Stalk-eyed Crustaceans. b. Hedriophthalms, or Sessile-eyed Crustaceans. c. Entomostracans, Crustaceans with shells. d. Cirripedes, Crustaceans with curled feet e. Xiphurids, Crustaceans with tails like swords. (a.) Stalk-eyed Crustaceans, or Podophthalms ; have eyes which are compound, placed on the extremity of two moveable stalks ; four antennas. The Stalk-eyed Crustaceans include two well- marked groups 1. Decapods, . . . Ten-footed Crustaceans. 2. Stomapodg, . . Crustaceans having the mouth between the feet. The Decapods have a large shield covering the head, and thorax, and anterior part of the abdomen ; their gills adhere to the bases of the posterior maxilliform feet, and are pyramidal, and covered by the shield : their feet are mostly in five pairs, but are sometimes in six pairs. The Decapods are usually divided into the following groups : Long tails, . . Lobsters, and Shrimps, and Cray fish. Short tails, . . Crabs. Anomalous tails, Hermits. The Lobsters are characterised by their first pair of fore feet being converted into large grasping forceps, while the second and third pair are provided with smaller forceps ; the tail is formed of a number of plates arranged transversely. The Shrimps have the first pair of feet thicker than the other four pairs, and two- fingered, with the inner finger very short and immoveable. The Crayfish (Palinurus] have no forceps on any of their feet ; they are large Crustaceans which inhabit rocky places in STALK-EYED CRUSTACEANS. 329 various seas, and are found in abundance in the Mediterranean, where they" sometimes attain a length of three feet. This Crus- tacean is described by Aristotle, under the name of Kdpaf}o?, as the type of its class ; it appears to be entitled to this distinction, both on account of its large size, and also on account of the fact, that it readily kills the Lobster, although it is not furnished, like that Crustacean, with a forceps claw, with which to attack its enemy. The Short-tailed Crabs have the tail, or posterior part of the abdomen small, and reflected forwards, while the shield covering the thorax is proportionately very large ; the first pair of feet is always provided with a forceps, and is sometimes very large, as in the Lobsters. The Hermits have the abdomen contorted and membranous, and endeavour to protect it by seeking refuge in dead univalves ( Trochus, Natica, &c.), which they carry along the shore upon their backs ; like the common crabs, they are furnished with pincers upon the first pair of feet, but have the fourth and fifth pair of feet undeveloped. These animals seize upon empty shells of different gasteropods, as they grow older, and when fully grown, are ge- nerally found, on our coasts, in the shells of the large whelk (Buccinum undatum). The ordinary forms of crabs, lobsters, shrimps, and cray fish, are so well known, as not to require illustration, and I have therefore selected, in preference, one of the Hermit or Soldier crabs, extracted Fig. i So. from his artificial house (Fig. 180.) Stomapods are much less known than Decapods ; they are dis- tinguished from them by the tendency to form a larger number of pairs of feet (often six, seven, or eight pairs), and by their gills being always uncovered, and often attached to the caudal feet ; 33 ELEMENTS OF NATURAL HISTORY. their shell also is thin or membranous, instead of being very hard, as in most of the Decapods. In some of the Stomapods there occurs an ex- traordinary develope- ment of the head and of the tail; the seg- ment containing the eyes, with their nerve ganglion, being pro- jected forwards in ad- vance of the rest of the head and thorax. This Fig. 181. peculiarity of the Stomapod Crustaceans is well illustrated by Fig. 1 8 1, which shows the Long-headed Shrimp (Lucifer typus], first described by Mr. Thompson. The Stomapods are all swim- ming Crustaceans. (b.) Sessile-eyed Crustaceans, or Hedriophthalms, have sessile eyes, and are divided into the following groups : 1. Amphipod&t . . . Crustaceans with feet in double row. 2. Isopods, .... Crustaceans with simple and similar feet. The Amphipods are sessile-eyed Crustaceans, having the first segment of the body distinct from the head, which carries a pair of foot jaws ; tail formed of several segments furnished with bifid feet ; body compressed and curved. These animals swim and leap with ease, always lying on their side ; and they are gene- rally marine. The best known of the Amphipods, to ordinary observers, are the Sand-hoppers (Fig. 182), which are very common along our coasts, and collect in swarms under every bunch of seaweed left by the retiring tide ; on disturbing the weed, the sand-hop- pers emerge like a cloud, jumping into the air, by the repeated bending of the body. They are carnivorous, and feed principally on worms, which they attack with avidity, and soon kill and SESSILE EYED CRUSTACEANS. 33 l devour. It is said that these little scavengers are capable of reducing a seal to the condition of a well- cleaned skeleton in less than two days. The fresh-water shrimp (Gammarus pulex) resembles the sand-hopper in the form of its body and in its mode of swimming ; they live on animal food, but, in its absence, content themselves with nibbling at roots, fruits, and other Fl S- l8z - vegetable substances. These Crustaceans have been swallowed, and have lived for some time in the human body. Certain of the lower Amphipods were long associated in a separate group, under the name of Lcemodipods. These Crusta- ceans have sessile eyes, and the first joint of the body united to the head ; the feet of this joint are placed far forward, under the head, which gives the animal the appearance of having feet on its throat, from which circumstance the family derives its name of Throat-footed Crustaceans. The Laemodipods do not swim, but creep on marine plants and animals in search of food. One of these singular animals is shown in Fig. 183, where it will be noticed that the second, third, and fourth pair of feet are furnished with two small bladders at the base ; these are gill vesicles, and the respiration of the animal is performed by means of them. The Isopods have sessile eyes, and head distinct from the segment bearing the first pair of feet ; the trunk is divided into seven segments, each furnished with a pair of undivided feet ; tail formed of several rings, supplied beneath with leaf-like gill feet ; antennae four, the lateral ones always like bristles. The well-known Wood-lice, and Sea-lice, are the best types of the Fig. 183. 33 2 ELEMENTS OF NATURAL HISTORY. Isopods ; the greater number of them live in water, and those which live on land require very damp situations, such as under the stones along the sea shore, or under the loose mortar of old walls ; they are capable of rolling themselves up into a ball, for protection when disturbed. Many geologists believe that the fossil Trilobites were Isopods, and quote in illustration the Serolis of the coast of Senegal (Fig. 184). In this animal the usual seven pairs of feet exist, but they are so short as to be ^S- l8 4- completely hidden under the edges of the dorsal rings. These Crustaceans are found at Terra del Fuego, as well as in Senegal, and the beach of many parts of the east coast of Patagonia is often covered with dead specimens. Captain King observed them swimming close to the bottom among the seaweed ; they moved slowly and gradually, quite unlike shrimps, and were never seen to swim near the surface. (c.) Entomostracans. This term is here used in a restricted sense to include all the groups of Crustaceans characterised by the possession of a bivalve shell of horny texture, or of a thoracic carapace, so large that it looks like such a shell. They are divided into 1. Phyllopods Crustaceans with leaf-like feet. 2. Cladocers Water Fleas. 3. Ostracods Bivalved Crustaceans. 4. Copepods Oar-footed Crustaceans. 5. Epizoans Parasitic Crustaceans. The Phyllopods have eight pairs or more of leaf-like thoracic gill feet, and sometimes additional swimming feet placed behind the gill feet ; they have also two compound eyes. I have se- ENTO MOSTRACANS. 333 Fig. 185. lected as an example of the Phyllopods (Fig. 185), the little animal called by the Germans the Fish-shaped-gill-foot (fisch- formige Kiefenfuss), called by us the Fairy Shrimp, and which is supposed to resemble the fossil Trilobites. It is found in stagnant water even in pools at the road side, and is so like the larva of the Mayfly, that it puzzled at one time the sagacious LinnaBus. Linnaeus first placed the Trilobites among the articulate animals under the name Entomolithm paradoxm ; Latreille regarded them as having a close resemblance to the Mollusks known as Chi- tons ; Wahlenberg revived the idea of Linnaeus, and placed the Trilobites among the Xiphurids ; while later writers have sought for affinities to Trilobites among the Isopods and Phyllopods; Van der Hoeven has strongly supported the view that regards them as gigantic Phyllopods. The Cladocers are little Crustaceans furnished with a bivalve horny shell, having a dorsal fold, but no hinge ; the head is free and projects from the shell, furnished with a beak ; foe feet are leaf -like, thoracic, and Jive in namber, and are used as gills ; the abdomen terminates in two bristles. In Fig. 186 a is shown the common "Water flea (Daphnia pulex] which abounds in water tanks, and forms an excellent study with the microscope. In spring its colour is reddish, and, from its great numbers, it some- times gives a tinge to the water of the entire tank. The Ostracods, or Potsherd Crustaceans, are little animals fur- nished with a bivalve shell, hinged at the back ; their feet are undivided, four or six in number, and useless for swimming, which is accomplished by means of two large jointed appendages, often regarded as posterior antenna. One of the commonest of the fresh water forms, Cypris, is shown in Fig. 1 86 c. The Cypris lays her eggs, about eighty, upon the stems of vegetables, 334 ELEMENTS OF NATURAL HISTORY. or in the mud, and it has been found, as among the Aphides, that the female Cyprids produced from these eggs are fertile without the assistance of the male Cypris. Many fossil forms of these En- tomostracans are known, and have been described by geologists. They extend back in time as far as the Devonian rocks, some members of which are called the Cypridina slates, in consequence of the immense numbers of little Cyprids preserved in them. Fig. 1 86. The Copepods or oar-footed Crustaceans, are characterised by an oval body, drawn out behind, and terminated by two bristles ; the swimming feet are in four pairs, and cloven each into two oars. In Fig. 186 b is represented one of the best known of the Copepods, the Freshwater Cyclops. These voracious little ani- mals abound in all stagnant pools, and do not hesitate, when hungry, to devour their own offspring. The Epizoic Crustaceans have a suctorial mouth, and the fore feet provided with hooks or suckers, for fixing the animal upon his prey ; when young, these crustaceans swim freely about by means of feet furnished with long hairs, and resemble the young animals of Cyclops or Copepods ; in their adult state they adhere parasitically to fishes, and are often deformed, and soft, with the body segments obliterated. These parasites vary greatly in ap- pearance with the fish they infest ; they are generally found in- side the gill covers, where they meet with a constant current of CIRRIPEDES. 335 fresh water, and they are supposed to change their form with the fish which they select as their host. (d). Cirripedes. This remarkable and well-defined group of Crustaceans becomes fixed to a rock or other substance in adult life, and is then enclosed in a multivalve shell, which is frequently calcareous ; no eyes ; six pairs of feet, with short fleshy stalks, and two cirri with many joints, and horny ; these cirri are used constantly by the animals, by extending them through the opening of the shell, for the purpose of introducing fresh water for respiration, and with it their daily food. Cirripedes are found in the seas of every part of the globe ; they attach themselves to rocks and timbers used for building piers and harbours ; but they es- pecially delight in a moving home, such as a log of floating timber from a shipwreck, the hull of a vessel, or turtles and whales ; it would seem as if their instinct taught them to attempt to counteract the disadvantages of their sessile life, by attaching themselves to objects endowed with a certain degree of independent locomotion. The best known of the Cirripedes are the Sea acorns (Balanus) and the Barnacles (Lepas]. The Sea Acorns or Sea Tulips, as they are called, have for their shells a sort of truncated cone, formed of pieces fitting upon each other with teeth ; this shell is closed above by a lid formed of four pieces arranged in two pairs, and which are part of the covering of the crustacean itself; the four separate segments that form the lid can be closed by appropriate muscles, and the open- ing between them leads into the sack in which the body is lodged. The native species of Balanus are all small, and cover the rocks at low water with a white crust of shells, that cut the feet of swimmers ; but the foreign species are well worthy of the title of Sea Tulips, from their large size and bright colours ; they may easily be seen by examining the bottoms of ships just re- turned from the Mediterranean or from India. 336 ELEMENTS OF NATURAL HISTOET. Fig. 187. The Barnacles or Goose Mussels (Fig. 187), illustrate well the structure of the Cirripede Crusta- ceans ; their bodies are covered by four pieces of shell which corre- spond to the four parts of the lid of the Sea Acorns ; while the single keel piece along the back of the Barnacle corresponds to the cal- careous tube of the Sea Acorn, and its fleshy stem may be regarded as a prolongation of the same. The Barnacles derive their name of Goose Mussel from a fable invent- ed by Scandinavian Monks, who asserted that a species of goose (Anas bernicla) had its origin from this Crustacean, and might be seen flying out from the Barnacle as a little gosling at certain seasons of the year ; and since there could be no doubt as to the fishy origin of the Lepas, the goose was pronounced to be good fish also, and was freely used in Lent, as a supplement to the meagre diet proper for that season. (e.} Xiphurids, or King Crabs (Fig. 188). These Crustaceans have six pairs of feet attached to the cephalo-thorax, the bases of which are spinous and surround the mouth, and serve it as masticators ; six other pairs of feet are attached to the abdomen ; these form semicircular plates, or swim- ming feet, to the last five of which the gills are attached. The body is composed of three parts ; a cephalo-thorax or buckler, carrying two pairs of eyes, one pair kidney-shaped, and compound (Fig. 188 ); and the other pair simple (b) ; an abdominal or dorsal buckler having the form of an ir- regular indented hexagon ; and a long sword-like tail arti- culated to the dorsal buckler, from which the animal derives its name. These Crustaceans are found in the Moluccas, and XIPHURIDS. 337 on the coast of Nova Scotia in North America. They are called Mimie by the Malays, and Umi-do-game by the Chinese, and are much prized as food when full of eggs, which in July and August almost fill the cephalo-thoracic buckler of the females, and are discharged by two large oviducts which open on the back of the first abdomi- nal segment. The King Crabs live in pairs, male and female, and are sold in pairs in the mar- kets of Batavia. The Malays eat the eggs with avidity, and the flesh pleases them and the Chi- nese. I have eaten the eggs, which are inferior to the roe of Fig. 188. the lobster ; but I regard the flesh as detestable, being almost as disagreeable as that of a young alligator. These Crabs live in a damp situation for more than a day out of the water, and when laid on their backs are unable to right themselves. Their tails form a powerful implement of de- fence, and are used by the Malays for spear-heads. Some geologists maintain that the King Crabs, of all living Crustaceans, are the nearest congeners of the Trilobites. E. Annelids, or Ringed, Worms. The primary division of the articulate animals, as has been stated, page 295, is into Arthro- pods, or articulates with jointed feet, and Worms. The Worms are divided into Annelids and Scolecids, in the first of which the true articulate structure of the body is more evident than in the second. The body of Ringed Worms is generally much elongated and cylindrical ; in some instances it is broader and oval in shape ; it 33 8 ELEMENTS OF NATURAL HISTORY. is divided by transverse folds into rings or girdles, which are often very numerous. The common Leech has 100 rings, and Phyllo- doce, one of the marine worms, has often upwards of 500 ring segments. The organs for movement consist of bundles of hairs sur- rounding a central bristle, as shown in the section of a ring seg- Fig. 189. ment (Fig. 1 89). One pair of such bristle-shaped feet is placed on the dorsal arch of the ring (d d), and the other pair (v v) is placed in a corresponding position on the ventral arch. Locomo- tion is effected by means of these bristles pushing against the ground, like the ribs of snakes. The nervous system consists, as in all the articulates, of a great ventral chain of double ganglions, through the collar formed by the first two of which the gullet passes : this anterior gan- glion is called, for this reason, the pre-cesophageal ganglion, and sometimes the cerebral ganglion. No Annelid ever possesses a heart comparable in developement with the heart of a Crustacean or Insect; but a system of vessels is found, through which a clear fluid, red or green in colour, and seldom containing corpuscles, is driven by pulsations from behind forward the dorsal vessel of this system acts as an arte- rial heart ; in some Annelids, a venous ventral vessel is also found, through which the blood returns from before backwards. This circulation is called pseudohcemal, and it is considered by Huxley ANNELIDS. 339 not as a true circulation, but as a modification of the "water vessel ' ' circulation found in the Scolecids and some of the Radiates. Respiration is effected by the skin only, or by external gills of very different forms, or by vesicles or bladders on the sides of the body. The external gills are well seen in the common Lug- worm (Fig. 190), where they consist of eleven pairs of arborescent organs, placed externally, and rather in advance of the middle of Fig. 190. the body. Some of the ringed worms, like some insects, are ca- pable of giving out a phosphorescent light, which appears to pro- ceed from the bases of their bristle-like feet. The Annelids are divided into three groups a. Sucking Worms. b. Bristle-bearing "Worms. c. Sipunculids. (a.) Sucking Worms have the body ringed, without bristles, and terminated by a prehensile cavity at one or at both ends ; no external gills. This division of Annelids includes the Leeches or Bloodsuckers ; these animals can convert their heads into a sucking disk, and some are furnished with three saw-like teeth meeting at angles of 1 20, with which they pierce the skins of their victims, previous to sucking their blood. Leeches have frequently an anal as well as an oral sucking disk, and they creep along the ground by affixing the suck- z2 34 ELEMENTS OF NATURAL HISTORY. ing apparatus, and by alternately contracting and expanding the body ; they swim rapidly in fresh water, with a serpen- tine and sinuous motion of the entire body. The most useful of the Leeches is the well-known Hinido medicinalis, which lives in fresh water, through the south and east of Europe ; and in winter conceals itself in mud, rolled up in a circular form. It lives exclusively on the blood of other animals, both vertebrate and invertebrate. The arrangement of the eyes of this leech is peculiar ; it possesses eight eyes arranged in horse-shoe form on the back of the head ; these eyes con- sist of four pairs, of which the first pair are placed on the first segment of the body, the second and third pairs are placed on the third segment, and the fourth pair of eyes on the sixth body ring. The Leeches are Hermaphrodite, the Spermducts opening on the twenty-fourth ring of the body, and the Oviducts opening on the twenty-ninth ring ; the leech, however, notwithstanding the possession of both testicles and ovaries, cannot fertilise its own ova ; and it requires the assistance of a second leech to effect its impregnation. The common Horse leech of this country is distinguished from the medicinal leech by the absence of teeth. Some of the tropi- cal leeches give poisonous bites ; thus the bite of the Hirudo Zeylanica is followed by tedious and dangerous ulcers. Many fresh water and even salt water fishes are attacked by species of leeches peculiar to each ; the Carp, the Tench, and the Ray have been especially noticed as thus favoured by Nature : fortunately for these fish, their leeches have no teeth, and are compelled to imbibe nourishment from their hosts, by simple suction. (#.) The Bristle-bearing or Setigerous "Worms are divided into two groups ; in the first of which respiration is effected by means of internal sacks opening by pores along the ventral side of the abdominal rings; and in the second, respiration takes place by means of external arborescent gills. &ETIGEMOUS WORMS. 341 The common Earth-worm may be taken as a representative of the first group. Respiration is effected in this animal by means of more than 100 vesicles opening on the abdominal surface; in addition to their use as respiratory organs, these vesicles also secrete a glairy mucus, that serves to lubricate the external sur- face. The Earth worm has its bristles, which are not retractile, arranged in longitudinal rows ; the bristles are short and stiff, eight in every ring, and on each side two pairs, so that eight rows of bristles run longitudinally down the body ; and there is also a dorsal row of hairs down the centre of the back. The intestinal canal of the Earth worm (Lumbricus] is straight and wide; it contains a crop (proventricle) and gizzard (mus- cular stomach) ; behind the gizzard, the intestine is divided by many transverse folds into caeca, or blind pouches, the secretion from which is supposed to correspond to that of bile. The intestinal tube becomes slightly narrower, after receiving the secretions from the caeca, and afterwards widens to its former dimensions. The second group of Setigerous Worms contains two divisions ; the first of worms living in fixed tubes, and having gills placed near the head, called Tubicolous or Cephalo -branchiate Worms; and the second containing the naked roving Worms ; with gills placed in rows upon their backs these Worms are hence called Roving or Notobranchiate* Worms. The Tubicolous Worms often form their tubes of grains of sand cemented by a glutinous substance; others again form their tubes of pieces of broken shells; and others, a.sSerptdaaud.Spirorbis, possess the power of secreting calcareous shells, in which they permanently reside these worms were until lately confounded with Mollusks for this reason. The Serpula (Fig. 191) has two large comb- shaped gills arranged like fans, with a cylindrical set of filaments * In the barbarous Graeco-Latin tongue used by Naturalists, tbis is ge- nerally called dor si-branchiate. 34 2 ELEMENTS OF NATURAL HISTORY. carrying an operculum, or lid, which closes the shell when the worm retracts its head. The shell itself is calcareous, twisted into an irregular convoluted spire, and is generally attached to the shells of some species of inollusk, as the oyster, sedentary in its habits. The Notdbranchiate Worms may be illustrated by the Lugworm already figur- ed (Fig. 190), and by the active little marine worm known to fishermen as hairy bait (Fig. 192). The Lugworm (Arenicola piscatorum), Fig. 190, has rudiments of feet, with a dorsal fasciculus of bristles, and a ventral row very minute, and incurved ; the gills are arborescent and placed in rows in the middle of the body ; the body is thickened Fig. iqi. forwards, in front of the gills, and becomes smaller behind the gills, where it has no rudiments of feet or of bristles. This worm lives in deep canals excavated in the sea sand, which the worm forms with its head, while the sand is swallowed and passed through the intestinal canal ; it is flesh- coloured or blackish, while its gills have a brighter colour, and it exudes a yellow fluid on being handled. The little worm called hairy bait (Nepththys, Fig. 192) has Fig. 192. its head truncated, and furnished with four small tentacles ; its rows of dorsal and ventral bristles or feet are separated by a row of strap-shaped gills. The beautiful animals called Sea mice belong to the group of SIPUNCULIDS. 343 Notobranchiate "Worms ; they are furnished with a row of horny scales, or plates, instead of tufts of bristles covering the dorsal feet ; the head is concealed and protected by the anterior scales, which project beyond it. It is generally five or six inches long, and one and a-half inch broad ; the bristles on the sides of the body are glistering, green and red, and showing the varying colours of the rainbow ; the back is covered with a dense felty covering of interwoven hairs ; when this covering is opened, fifteen nearly circular plates are seen on each side, which partly cover each other, the central being the largest. If two consecu- tive plates be separated, there are seen on the body segment, or ring that lies between them, small longitudinal nodes separated by a pit, and furnished on the outer and back side with comb- shaped gills that look as if they had been torn at the margins. (c.) Sipunculids The Siphon worm (Sipunculus, Fig. 193), and Fig- i93- its allies, classed by former naturalists with the Radiates, are now placed among the Annelids, of which class they constitute a distinct order ( Gephyred). F. Scolecids. The Scolecids form the last and the lowest di- vision of Articulate animals ; and are divided into the following groups : * a. Rotifers Wheel animalcules. b. Turbellarians. c. Tretnatodes Flukes. d. Cestodes Tapeworms. e. Nematodes Threadworms. f. Acanthoeephalids. g. Gordians. * VicU Huxley's Elements of Comparative Anatomy. 344 ELEMENTS OF NATURAL BISTORT. Of these subdivisions of Scolecid worms, the last five are pa- rasitic, and exhibit anomalies of structure and of developement, such as might be expected from creatures living under such ex- ceptional conditions. Most of these animals agree in the possession of what is called the water vascular system, formed of a remarkable set of vessels, communicating with the exterior medium by means of one or more apertures situated on the surface of the body, and branching out, more or less extensively through the interior of the substance of the body of the animal itself. In none of these Scolecids has any true circulatory apparatus been discovered. The water vascular system may be said to perform'the offices of circulation and respiration by means of the same system of organs. The nervous system in the Scolecids consists of only one or two closely approximated ganglions. (a.) Rotifers, or Wheel Animalcules, are microscopic Scolecids, con- tractile, crowned wiih vibrate cilia, at the anterior part of the body, which resemble a wheel revolving rapidly ; intestine dis- tinct, having a mouth and an anus ; sexes distinct, oviparous in Fig. 194. winter, viviparous in summer. The general appearance of these animalcules under the microscope may be understood from Fig. 194, which represents the Eotifer called Bra- ROTIFERS. 345 chionus (a, b), characterised by having two rotating disks, and finger-shaped jaws, and the Eotifer called Stephano- cero8(c~). The rotation of the disk is an optical illusion caused by the successive motion of the cilia on the margin of the disk; the motion of the cilia is subject to the control of the animal itself. The Rotifers are capable of contracting their bodies, so as to assume an oval shape, and many of them are furnished with a tail-like appendage, which can be drawn in and out, like a tele- scope, and by means of which the animalcule attaches itself to the place selected for its fixed abode. The motion of the vibra- tile cilia serves for a double purpose : when the animal is fixed, they form a perpetual current of water setting in towards the mouth, which is furnished with lateral jaws like those of crusta- ceans or insects, so that the smaller animalcules, called Infusories, are carried by this current into the mouth of the Rotifer, and there destroyed ; on the other hand, when the animal is not fixed, the vibrating, rotatory, movement of its cilia acts like a ship screw of the most delicate and perfect description (because it is flexible, and so takes the form of the screw of least slip), and pro- pels the little creature from place to place until it suits his pur- pose to rest and seek his food. The sexes are distinct in Rotifers, the female being the most important ; she is furnished with an oesophagus, a stomach, pan- creatic glands, and caecal cells that serve the office of a liver ; in fact all the digestive machinery requisite for the enjoyment and assimilation of a great variety of food ; her male partner, on the con- trary, has neither mouth, nor intestine, nor anus ; he never eats, because his life is destined to be so short, that it is not worth while to provide him with a stomach or mouth ; his sole business in life is to secrete sperm for a short time, and as soon as he has fertilized the female, he must die. The Rotifers, how- ever, cannot be accused of the cruelty of the old maid Bee workers, who kill the drones when they have done their duty ; 34-6 __ ELEMENTS OF NATURAL HISTORY. nor of the barbarity of the matron Spider, who eats her husband after she has embraced him, coolly performing the part assigned by Danaus to his daughter Hypermnestra : " I nil," quod he, "have none excepcioun." And out he kaughte a knyf as rasour kene. " Hyde this," quod he, " that hyt be not ysene ; And whaune thyn housbonde ys to bedde goo, "While that he sleepeth kut hys throte atwoo."* There is something most hateful to our higher feelings in the instinct of the spider that eats her mate, or in that of the lioness that devours her cubs, when unable to suckle them ; in order that no particle of assimilable food shall be allowed to go to waste. The economy of material, and of food, shown in such strange instincts, teaches us that nature has her dark as well as her bright side, and that she presents, in her lower forms, in- stincts and passions, which, if imitated by man, would justify cruel- ties towards the poorer members of society, such as have not (as yet at least) entered into the hearts of political economists to conceive. An Egyptian fable informs us that the votaries of the goddess Nature were divided in opinion, as to whether she was trans- cendantly beautiful or hideously ugly ; and that, in order to keep up the mystery on this subject, she always wore a thick veil over her face ; For with a veil that wimpled everywhere, Her head and face was hid that mote to none appear. That, some do say, was so by skill devised, To hide the terror of her uncouth hue From mortal eyes that should be sore agrised, For that her face did like a Lion show, * Legende of goode women. Chaucer. TURBELLARIANS. 347 That eye of wight could not endure to view : But others tell that it so beauteous was, And round about such beams of splendour threw, That it the sun a thousand times did pass, Nor could be seen, but like an image in a glass."* (b.) The Turlellarians. These animals, like the Rotifers, are not parasitical, but they deserve to be so, from their degraded structure. They possess a cylindrical, or depressed body, generally without segments, but having transverse wrinkles, and covered with vibratile cilia. They are divided into two families, of which the Planaria and the Nemertes are cha- racteristic types. They are called Turlellarians from the currents and rotatory movement developed in the surround- ing water, by their cilia. The Planaria (Fig. 195) has a digestive canal with one aperture only, and without an anus ; body without ring segments. They possess a mouth situated near the centre of the body, on Fig. .95- Fig " I96 ' the ventral surface ; and the intestinal canal branches off in various directions through the jelly-like mass of the body, ter- minating always in blind pouches. The Nemertes (Fig. 196), or Long sea worm, often reaches the extraordinary length of ninety feet, and is found on the sea * Faerie Queen Mutabilitie. 34 8 ELEMENTS OF NATURAL HISTORY. shore, coiled up in gordian knots, under the loose stones. It has a simple intestine, with an anterior mouth, and terminal anus, and is roundish, or slightly depressed, with imperfect marks of body rings the head is distinct, and it possesses from four to fourteen eyes, arranged in pairs. (c.) The Trematodes or Flukes, are internal worms, infesting the body of man, sheep, and especially fishes. They have a general resemblance to the Planarians. The body is depressed or roundish and soft ; they are furnished with suctorial disks, and have a branching intestinal canal ; one of the suctorial disks leads into the mouth, and the others are blind. They are found abundantly in the sheep's liver, and in the gall-blad- der of Man, the Ox, Deer, and others ; some of them, also, live gregariously in the eyes of certain fishes ; others are found in pairs, lying in elastic tumours under the skin of the belly and thighs of Finches ; while those that live on the skin, or in the gills of fishes, are almost countless. (d.) The Cestodes, or Tape Worms, are better known than liked ; they possess an elongate, flat, jointed body, well described by the term Tape worm ; they have no mouth, but the head is furnished with suctorial pores. Three kinds of this dreaded pest infest the small intestines of man ; the Russian Tape "Worm (Bothriocephalus latus}, the common Tape Worm (Teenia solium), and a third species, scarcely less abundant (TcBnia mediocanellatd]. The Russian Tape Worm is found abundantly in Lapland and Russia, in Man, and in the Polar Bear ; it is broader than the common Tape Worm, and attains a length of twenty feet. The common Tape Worm (Tcenia solium), or Internal Worm that sits enthroned in state, called by the French ver solitaire, owes both his Latin and his French name to the mistake, that in the same person one such worm only can be found. It infests the people of Western Europe, and is occasionally to be met with in the same intestine, in company with its rival, the Bothriocephalus latus. TAPE trOEVS. 349 It has been satisfactorily proved, that the internal worms, called Cystic Worms, from being enclosed in a bladder-like vesi- cle, are really the undeveloped forms of the dreaded Tape worms, waiting for admission into a suitable host, such as Man or the Polar Bear, for their further developement. These undeveloped worms are called Hydatids, and are met with in many domestic animals, in the liver, the abdominal cavity, and even in the heart and brain. The Cystic worms of the pig are believed to be the undeveloped Tape worm of Man ; and a Cystic worm found in Rats has been proved to be the same as the developed Tape worm peculiar to Cats ; thus the animals we devour avenge their deaths by filling our intestines with living mementoes of parasites that once troubled themselves, and thus their very enemies avenge their slaughter. (e.} The Nematodes, or Thread Worms, contain several species interesting to man from their attacks upon him. They possess a mouth, and amis terminating an intestine suspended in a distinct abdominal cavity ; sexes distinct ; body round, elastic, sometimes thread-shaped. The Ascaris lumbricoides, or Round worm, infests the intes- tinal canal of man, and attains the length of fifteen inches. It is named lumlricoides from its external resemblance to the Earth worm. It is considered to be different from similar worms that infest the intestines of the Horse and Pig. In children, it is sometimes vomited, having made its way upwards into the stomach ; and it has been known to creep out of the nose of a sleeping child; and has been even accused of causing death, by mistaking the windpipe for the gullet, in its explorations, and so causing suffocation. The Oxyuris vermicularis lives in bundles in the large intes- tine, especially of children, and never wanders far from the anus ; it often causes serious nervous symptoms, even epilepsy ; but its low tastes cause its destruction, for as it never leaves the large 350 ELEMENTS OF NATURAL HISTORY. intestines, the skilful disciple of Esculapius attacks the colony with a turpentine glyster, and speedily routs it in dismay. The Guinea worm (Filiaria Medinensis) lives in the cellular tissue, under the skin of man, especially in the legs, and attains a length of ten feet ; it is endemic in Curaqoa and in some hot countries of the Old "World, and often causes severe pain. It is viviparous, and it is remarkable that the male worm has never yet been found ; all the specimens examined by naturalists, hitherto, having proved to be females. (/.) Acanthocephalids, or Spiny-snouted Entozoans. These worms have a roundish bladder-shaped lody, marked with transverse wrinkles ; no mouth or intestine ; proboscis retrac- tile, and armed with recurved hooks ; sexes distinct. They are found in the intestinal canal of many birds and fishes ; also in that of the Pig and the Seal. Upwards of i oo species of Echinorhyncus have been described, one of which (E. por- rigens) is common to the Eider Duck, and lesser Rorqual Whale ; it is found in the duodenum of that whale, where its presence is indicated by large fleshy papillae in the mu- cous membrane of the intestine ; the openings of these papillae from the intestine lead into tubular cavities, situated obliquely between the mucous and the muscular coats of the gut, in each of which lies ensconced a formidable looking Echinorhynchus. Specimens of this dreadful entozoon have been recently found in the intestines of the short-tailed monkeys, and, let us hope, may yet be found in man. (ff.) The G&rdians, or Hair Worms, are hair-like, extremely slender and elastic; anus none; sexes distinct. These worms are found commonly in summer time in ponds and ditches, and so closely resemble horse's hairs that they are believed by schoolboys and country folk to be living hairs. They are scarcely separable from the lower Nematodes. In the imma- MOLLUSKS. 351 ture stages of their existence, they are parasites in the interior of certain insects, especially Water Beetles, where they grow to a length of ten or eleven inches, and then escape from the body of their victim, to seek some sheltered pool in -which they may lay their eggs, which may be found fastened together in long chains. 3. Mollusks. The Mollusks form the second grand subdivi- sion of invertebrate animals ; they possess a body covered by a skin, soft and constantly moist, to which muscles are attached, and in which, or by which, a calcareous secretion, forming a shell, is usually produced. This external skin or mantle encloses both the intestines and the nervous ganglions. The Nervous System in Mollusks consists of distinct gan- glions, connected by nervous filaments, and never so symmetri- cally arranged in pairs, as among the articulate animals. The difference between the nervous systems of the articulates and mollusks may be seen from a comparison of Figs. 109 and no. Many naturalists divide the Mollusks into two groups, according to the arrangement of their nerve ganglions ; in the first division, which embraces the most highly organised of these animals, there are always three principal pairs of nerve masses, united into gan- glions, and called, respectively, the cerebral, the parietosplancJmic, and the pedal ganglions : these ganglions preside respectively over the senses, the digestion and reproduction, and the locomotion of the Mollusk ; in the second division of mollusks, sometimes called Molluscoids, the nervous system is greatly simplified, being reduced to a single principal ganglionic mass, which usually de- taches a nervous collar round the ossophagus, and affords origin to other nerve filaments distributed throughout the body. As a consequence of this imperfect developement of the nervous system, the functions of the animal life are less developed than in the articulates, and the movements of Mollusks are, on the whole, creeping and slow, and those of them that possess a 35 2 ELEMENTS OF NATURAL HISTORY. springing motion, as certain Bivalves and the Cephalopods, exert their muscular power in a more uncertain and irregular manner than the higher articulates. The Vegetative or visceral life of the Mollusks is much more per- fect than their animal life ; most of them possess an arterial heart, which receives the blood from the gills or lungs, and distributes it by arterial tubes to the different parts of the body (Fig. 1 79). Capillary blood vessels are wanting, and the veins are replaced by sinuses or cavities in different parts of the body, in which the blood collects before returning to be oxidised in the gills. The arterial heart of the first or highest division of the Mollusks shows its superiority to the second division, as clearly as did the nerve ganglions. In the higher Mollusks, there is a distinct auricle and a distinct ventricle in the heart ; while in the lower forms (Mol- luscoids), the heart is saccular, and not divisible into an auricle and a ventricle. 4. Classification of Mollusks The Mollusks are divided into the following classes : A. Cephalopods. B. Pteropods. ( > Mollusks proper. C. Gasteropoda. | D. Lamellibranchs. / E. Brachiopods. } F. Tunicates. > Molluscoids. G. Polyzoans. A. Cephalopods. The Cephalopods are Mollusks with a dis- tinct head, having the organs of motion .(tentacles') surrounding the mouth in a ring ; gill cavity, open in front ; sexes distinct ; res- piration by gills; marine. Locomotion is effected among the Cephalopods, partly by means of their arms or tentacles, but chiefly by means of the propulsion of water from the gill sack, through a funnel placed under the head ; the mantle or skin sur- rounds the body loosely, forming a large gill sack, opening to the external water by means of an aperture under the head (in the CEPHALOPODS. 353 middle of which the funnel is placed, furnished with muscular walls ; by the sudden contraction of the mantle, the water con- tained in the gill sack is forced out through the funnel, and the Cephalopod is suddenly jerked in the opposite direction by its reaction. The intestinal canal and the genital organs discharge their contents into the large gill sack formed by the mantle. The Cephalopods are more symmetrical than most other Mollusks, their right and left sides being equally developed ; they have powerful jaws, furnished with horny curved points, like a parrot's bill, and a large fleshy tongue ; their eyes and optic nerves are very large, and their eyes are placed on the side of the head ; their senses are acute ; and they are predatory in their habits, living upon shell fish, crabs, and fishes. The Cephalopods are divided into two groups, according to the number of their gills, which is either two or four ; these gills are conical, and run obliquely upwards, situated one at each side, in the base of the gill sack. These two divisions are called a. Dibranchiate Cephalopods. b. Tetrabranchiate Cephalopods. In the Dibranchiate Cephalopods, a branchial heart is situated at the base of each gill, to propel the blood into that organ ; these two hearts are in addition to the usual arterial heart, and are wanting in the Tetrabranchiate Cephalopods. In both divisions, there are found, surrounding the large venous stems that convey the blood to the gills, spongy appendages, of a yellowish brown colour, with blind follicles, which are regarded by anatomists as fulfilling the office of kidneys. (.) Dibranchiate Cephalopods. Swimming, naked, Mollusks; head distinct ; eyes sessile, prominent ; mandibles horny ; arms eight or ten, furnished with suckers; body round or oval, usually with a pair of fins ; gills two, furnished with venous hearts; ink gland always present ; wall of the funnel entire ; test in- ternal (Argonautd excepta], horny or shelly, with or without chambers. 2 A 354 ELEMENTS OF NATURAL HISTORY- The Dibranchiate Cephalopods are also called Acetaluliferous, from having suckers upon their tentacles ; they are subdivided into (a) Octapods, and (y3) Decapods, according to the number of their arms. (a.) The Octapods contain the two families of Argonauts, and Polypes, the first of which is characterised by its females possessing external shells. The ink bag is a tough and fibrous organ, opening into the gill sack cavity near the point of discharge of the intestine ; and its secretion is used by the Cuttle fish to darken the water, and so cover its re- treat, in flying from a pursuer. The Argonaut (Fig. 197) is an Octapod, whose female is Fig. 197. furnished with a single chambered shell, secreted by the two dorsal arms ; the figure represents the Argonaut, swimming by the expulsion of water through the funnel of the gill sack ; the transparent shell of this beautiful animal is not fitted to the body, nor attached to it by shell muscles ; it is essentially an ex- ternal appendage secreted by the arms ; the animal swims like other Cuttle fish, by discharging water through its funnel, and when feeding, walks upon the sea bottom, with its head and arms down, and shell inverted. The Argonaut has four species still living, and one of these, which is found in the Chinese seas, is also found fossil in the Sub-Appennine and Tertiary beds of Piedmont. THE ARGONAUT. 355 Aristotle was well acquainted with the Mediterranean species, which he thus describes: " The Argonaut is a polype singular in its nature and in its actions, for it sails upon the surface of the sea, having first as- cended from the deep water ; it ascends with an inverted shell, in order that it may go out more readily and sail in the empty shell ; when it reaches the surface it turns the shell over. It has between its tentacles a web like that of web-footed birds, except that theirs is coarse, and this is thin, and like that made by a spider; this it uses for a sail when the wind blows, and it employs two of its tentacles instead of a rudder. If it be frightened, it goes down, having first filled the shell with sea water." The Polype resembles the other Cuttle fish, in having no shell, but it differs from them in the number of its tentacles, which are eight instead of ten, and are symmetrically arranged round the head. It is a most unamiable and voracious brute (Fig. 198), devouring shell fish, and even the formidable Cray fish. Aristotle made many accurate observations on the Polype, which show that he well knew the diffe- rence between this Octapod and all the other Cuttle fish. He mentions that they are the only Cuttle fish that come ashore, that they live in holes in the rock, which are found by the fishermen observing the shells broken by the Polype for food ; and also states that the Cray fish, if caught in the same net with a Polype, will actually die of terror. Homer compares Ulysses holding on to the rock so tenaciously, as to leave the skin of his fingers behind, to the polype torn from its hole, and carry- ing pieces of small stones attached to its suckers. 35^ ELEMENTS OF NATURAL HISTORY. (i>t; ^' ore irov\viroSoQ, OaXdju^ irpoq KOTvXrfdovofyiv TrvKivai Xai'yytc t\ovrat, we rov Trpof Trsrpycri Gpaatiatav airb \tipStv pivot d.TTtpvQfv, rbv dt f*iy Operculate emails. 7. Aciculidae ) GASTEROPODS. 363 The land snails are so well known that it is unnecessary to describe them ; in Fig. 204, a, is shown a typical Slug (Limax), having a small shield-shaped mantle, containing a rudimentary Fig. 204. nail- shaped shell concealed by the mantle; in Fig. 204, b, is shown the manner in which the Slug, when alarmed, withdraws his head from observation beneath the shelter of the mantle. (c.) The Opisthobranchiate Gasteropods have no shell or a very rudimentary one; gills arborescent, not enclosed in a gill chamber, but exposed on the back and sides, towards the hinder part of the body, behind the heart ; hermaphrodite. These animals are called popularly Sea slugs, and have the power, when alarmed, of retracting their gills and tentacles, so as to present the appearance of a shapeless mass. The nervous system of pairs of ganglions corresponding to the cerebrospinal system of the higher animals, is well developed in the Sea Slugs. They possess a pair of olfactory ganglions at the base of the tentacles, and a pair of optic ganglions, at the pos- terior border of the cerebral or cephalic ganglion, which lies in front of the gullet ; the auditory capsules, formed of little vesi- cles filled with fluid, and containing earstones (ptoUtlts) in con- stant vibration, are attached to the cephalic ganglion itself, just behind the optic ganglions ; these all lie in front of the gullet, which passes through the ring or collar formed by nerve fila- ments connecting the cephalic ganglion with the pairs of buccal 3 6 4 ELEMENTS OF NATURAL HISTORY. Fig -205. and pedal ganglions, called mbwsophageal ; behind these come the branchial pair of ganglions, and lastly the great single gan- glion called visceral. I have selected two of the Sea Slugs to il- lustrate the entire group. In Fig. 205 is shown one of the Sea lemons (Doris), characterized by plume-shaped gills placed in a circle in the middle of its back, and by two blunt tentacles placed rather far back, behind which the sessile eye specks may be seen in young specimens. In Fig. 206 is shown an JEdis charac- terised by rows of bud-shaped out-growths arranged down the back, and by long and non-retractile tentacles, (rf.) The Heteropods, also called Pter abran- chiate and Nucleobranchiate Gasteropods, consist entirely of oceanic forms, which swim at the surface instead of creeping at the bottom of the sea ; their foot is compressed into a fin, and furnished with a sucking disk, by means of which they attach themselves to float- ing seaweeds ; their gills are comb-shaped and placed on the back, being often protected by a delicate glassy keeled shell ; they frequently attain a considerable size, and feed upon small Sea nettles and Pteropods. The fossil forms called Bellerophon and Maclurea are considered to have be- longed to Heteropods of considerable size. In Fig. 207 is shown one of the Garinarias, swimming upon its back. It is so transparent that the intestinal canal can be seen ter- minating in the dorsal gill chamber, and protected by a curved shell (s~) ; on the ventral surface is seen the fin-shaped HETEROPODS. 365 disk, converted into a swimming organ, and furnished with a sucker at/. Fig. 207. D. Lamellibranchs. The Lamellibranchs form, with the Brachiopods, the Bivalve shells of Linnaeus ; and are sometimes called Acephals, because they have no heads ; they are called Lamellibranch, from the arrangement of their gills in leaves, as is well seen in the so-called "fringe" or "beard" of the oyster. The body of these Mollusks is more or less completely enveloped in the loose mantle which surrounds it, and secretes the bivalve shell ; frequently this mantle has an opening in front through which the foot, Fig. 208, /, emerges, and another opening Fig. 208. behind, through which the branchial and anal siphons are ex- truded (b, a) ; the lower of these siphons admits a constant cur- rent of water into the cavity of the loose mantle ; this water passes forward, over the gill plates, and reaches the mouth, which is placed in front, above the foot/, and is then carried backwards along the dorsal surface, receiving the anal excretions behind the hinge; and finally leaves the mantle by the efferent or anal siphon, marked a in Fig. 208 ; thus the same current of water that oxidates the blood in the gills carries the particles of food 366 ELEMENTS OF NATURAL HISTORY. on which the bivalve subsists, to the mouth, and circulating again backwards, serves as the sewer that carries off all the impurities of the system. Many of the bivalves do not possess siphons, but the current of water sets in and out of the mantle, and performs a circulation identical with that which occurs in Fig. 208. The Lamellibranchs have always a heart with a single ven- tricle ; sometimes two such hearts remote from each other (Area); in the latter case, the two hearts fulfil the same office at the dif- ferent sides of the body, and, like the single heart, are always arterial, receiving the blood from the gills, instead of forwarding it to those organs ; there are sometimes two auricles in the heart ( Anodon), and sometimes only one, as in the Oyster. The cerebral, pedal, and splanchnic pairs of ganglions are always present ; pre- siding over special sensation, locomotion, and organic life, respec- tively. The symmetry of the Lamellibranchs is a right and left hand symmetry, for the right and left halves of the mantle each secrete a distinct shell, and in this respect their symmetry is es- sentially distinct from that of the Brachiopods, in which the mantle lobes correspond to the anterior and posterior regions of the body, so that the valves of their shell are called dorsal and ventral, instead of right and left valves. The natural families of the Lamellibranchs are grouped to- gether, on two principles of classi- fication ; according as they have, or have not, siphons ; and accord- ing to the shape of the line called thepallial line. This line is formed by the muscular fibres of the mar- gin of the mantle, where it is attached to the shell ; if the mar- gin of the mantle form a conti- Fl &' 20 9- nuous line, as in Fig. 209 (Cyprina), the shell is called integro- palliate, and the animal that lived in it either had no siphons, or those siphons were not retractile ; if, on the contrary, the La- LAMELLIBRANCHS. 367 mellibranch possessed a retractile siphon, the margin of the mantle shows a sinus at its posterior rim, which marks the po- sition of the muscular fibres employed to draw it back, and also measures approximately the length of the siphon itself: in such a case the shell is called Sinupalliate , and the general form of the pallial line is shown in Fig. 2 1 o ( Cytherea). The shell here figured is one of the Venus family, which is con- sidered to be the most highly or- ganised of the Bivalves. If we arrange the families of the bivalves according to their relationship and affinity to each other, setting out from the Venus family, we shall Fig. 210. find that two distinct lines, or streams of relationship, carry us from the Veneridce ; in one direction, to the gaping shells and boring shells, which are related to the Ascidian Mollusks ; and in the other direction, to the Oysters, which are related to the Bra- chiopods. FIBST STREAM OF BELATED FAMILIES. A. Lamellibranehs with Sinupalliate Shells. 1. Veneridae The Venus family. 2. Mactridse The Mactra family. 3. Tellinidaj The Telline family (Fig. 208). 4. Solenidae The Rasor shells. 5. Myacidse The Gaping shells. 6. Anatinidse The Duck-bill shells. 7. Gastroch*nid3B > The Boring 8neUs . 8. Pholadidse ) SECOND STREAM OF BELATED FAMILIES. A. Lamellibranehs with Sinupalliate Shells. i . Veneridae The Venus family. 3<58 ^ ELEMENTS OF NATUEAL HISTORY. B. Conchifers with Integro-palliate Shells, a. With Siphons. 2. Cyprinidae The Cyprina family (Fig 209). 3. Cycladidae 4. Lucinidse ,, 5. Cardiadae The Cockle family. 6. Tridacnidse The Clam shells. 7. Hippuritidae Altogether fossil. 8. Chamidse b. Witho^^t Siphons. 9. TJnionidae The River Mussels. 10. Trigonidse The Trigonias. 1 1 . Arcadae The Ark shells. 1 2. Mytilidse The Mussel family. 1 3. Aviculidse Wing shells. 14. Ostraeadse The Oyster family. E. Brachiopods. These are marine Mollusks, better known by their representatives in the fossil than in the recent state ; they have gills attached to the mantle, which is composed of a dor- sal and a ventral lobe ; and are furnished with two long spiral arms, which act as labial tentacles, and bring food to the mouth, which always lies at the base of the arms ; the shell is bivalve, but the valves are, like the lobes of the mantle, dorsal and ven- tral, instead of right and left valves. These shells are called Lamp shells by the older Naturalists, from the hole in the apex of the ventral valve, which allows the passage of the pedicle by which it is attached to the rock, resembling the wick hole in an Antique Lamp. The general form of the Lamp shells is shown in Fig. 211, which represents a fossil species of Terebratula. The mechanism by which the shell is opened in the Bra- chiopods differs widely from that used in the Lamellibranchs. The shell of Lamellibranchs is closed voluntarily by adductor muscles, and opens without effort by its ligament. In Brachio- pods, however, muscles both open and close the valves, which BRACHIOPOD& 3 6 9 are thus independent of the elasticity of the hinge liga- ment. Fig. zii. The Brachiopods possess a "water vascular" system, fur- nished with two or four false-hearts, freely communicating with the surrounding medium, but having no connexion with the blood vessels, properly so called : this remarkable water-vascular sys- tem serves as an excretory channel, to convey away effete tis- sues, and the products of the reproductive organs ; it is found, under variously modified forms, in most Mollusks, among which it seems to perform the office discharged by the kidneys in the other animals. The Brachiopods are divided into the following families, most of the species of which are altogether fossil : 1 . Terebratulidae Lamp shells. 2. Spiriferidae 3. Rhjnchonellidae 4. Orthidae 5. Productidae 6. Craniadse 7. Discinidae ., 8. Lingulidae ,, F. Ascidians. The Ascidian Mollusks, or Tunicaries, are so called from their resemblance to a leathern bottle or bag, with two apertures (Fig. 212), o and a, which give them the appear- ance of a two-necked jar. One of these apertures, called the oral 2 B 37 ELEMENTS OF NATURAL HISTORY. aperture, 0, the so-called branchial sack, the entrance to which is often surrounded with a fringe of tentacles, admits a constant current of water, and leads into a large pharyn- geal cavity ; the gullet, stomach, and intestine, follow the pharynx in due order, and terminate in a chamber leading to the second aperture of the Ascidian, called the atrial or anal aperture, a, through which a stream of water constantly passes outwards. This water passes from the sides of the pharyngeal sack or gill chamber, by means of the water-vascular system, through the body walls, into the efferent or atrial chamber, from which it escapes again into the surrounding me- dium ; and thus a perpetual circulation of water is established, carrying food into the stomach, oxidating the gills, and removing all the effete matters from the body tissues, in the manner of a kidney ; which, even in the higher animals, is little more than a well constructed blood filter. The Ascidians possess a distinct heart, of very simple con- struction, for it consists only of a muscular tube, without valves, and open at both ends. This heart behaves in a manner else- where unknown in the animal economy, for it works at regular intervals, alternately in opposite directions, forming, literally, a tidal circulation, in which the two ends of the heart are alter- nately venous and arterial. All the Ascidians possess one nervous ganglion placed in front of the oral aperture. G. Polyzoans. The Polyzoans are well known to geologists as the so-called Lace Corals, and to sea-side collectors, as the Sea Mosses; they are minute social Mollusks, living together in communities, the common frame-work of which resembles seaweed of a horny constitution. One of the commonest of these Mollusks is shown in Fig. 213, which represents the Flustra, or Sea Mat of the British coasts. On examining the POLYZOANS. 371 J< lustra with a lens, its surface is found to consist of a great number of symmetrical cells, placed close to each other, like those of a honey-comb ; and each of these cells is found to be occupied by an individual mollusk, which was formerly regarded as a Zoophyte, but which is now well known to be much more highly organised than any Zoophyte. The Polyzoans have long tentacles, furnished with vi- bratile cilia, which surround Fig. 213- the mouth, and carry towards it a constant stream of water; they have an intestinal canal folded back upon itself, so as to open externally near the mouth ; and between the oral and anal aper- tures the solitary nerve ganglion is placed ; the anterior part of the Polyzoan is retractile within the posterior by inversion. The general structure of the indivi- dual Polyzoan is shown in the magnified Fig. 214, which repre- sents the Plumatella, one of the fresh water Polyzoans. No heart has yet been found in the Polyzoans, the results of digestion seeming to pass directly through the walls of the intes- tine, and to become mixed with the perivisceral fluid. r . Radiates. The Invertebrate animals, according to Cuvier, are divisible into three groups Articulate, Molluscan, and Ra- faate into which last group were thrown by Cuvier all the invertebrate animals that are neither articulate nor molluscan. 2 B 2 Fig. 214. 37 2 ELEMENTS OF NATURAL HISTORY, In the Radiate animals a special nervous system is not always present ; when found, it appears as a ring surrounding the mouth, from which ring, nerves proceed like rays, to the cir- cumference of the body. Among the Radiates, Cuvier ad- mits that there are included some forms that cannot he called Radiate in any proper sense of the term ; " the lowest families," he says, "present only a sort of homogeneous, sensitive, and mo- bile pulp." These lower forms, which are non-radiate, have, by common consent, been thrown into a separate group, called Proto - zoan ; and the group of Radiates now contains only such animals as present the typical Radiate structure. It is divided into two minor groups A. The Echinoderms. B. The Ccelenterate Animals. Professor Huxley and other naturalists would remove the Echinoderms from the Coelenterates, and place them with the Scolecid worms, with which they show many affinities in their earlier stages of growth ; it is more convenient, however, for the purposes of an elementary work, to leave the Echinoderms among the Radiates of Cuvier. A. Echinoderms. This name was originally given, after Aris- totle, to the Sea Urchins only, but is now extended, to embrace the Sea Stars, Sea Cucumbers, and others. They form an exceed- ingly natural class, and may be readily distinguished from all other animals. They are characterised by an intestinal canal, hanging free in the cavity of the body, usually long and tortuous, or furnished with lateral caeca when it is short. In all the adult Echinoderms there exists a ring-like or poly- gonal ganglionic cord of nerves surrounding the mouth, and send- ing filaments to the locomotive organs. Locomotion is effected in many Echinoderms by a peculiar arrangement : if we examine, for example the under surface of ECHINODERMS. 373 one of the rays of a Sea Star, we shall find a groove (Fig- 215), furnished with four rows of perforations, like pin holes, in alter- nate rows, through which small fleshy cylindrical feet can be extruded, at the pleasure of the animal ; this groove is called the Ambulacrum by Linnaeus, from a fanci- ful resemblance to a walk among trees, and the little feet are called ambulacral feet. These feet are hollow cylinders communicating internally with the water-vascular circulation, which is developed on a grand scale among the Echinoderms. The fluid can be forced from the water-vascular tubes into the ambulacral feet, or withdrawn at pleasure ; and the animal progresses slowly by the alternate protrusion and retraction of these feet. The rows of feet are gene- rally two or four in number. In addition to the other vessels of the ambulacral, or water- vascu- lar system, a peculiar tube, called the madreporic canal, ter- minating in the ma- driporiform tubercle, is found in the Sea Ur- chins and Sea Stars. The madreporiform tu- bercle is shown in Fig. 216, a. The Echinoderms en- joy a symmetry which is both radiate and bilate- ral, and may properly be named an elliptically ra- diate symmetry ; while the lower forms of Ba- diates, among the Coelenterate animals possess no bilateral sym- metry, and may, therefore, be said to have a circularly radiate symmetry. In Fig. 2 1 6, a line drawn from the centre of the Fig. 216. 374- ELEMENTS OF NATURAL HISTORY. Star rays to the madriporiform tubercle, a, marks the plane of bi- lateral symmetry, or axis of elliptical symmetry ; and in like manner, in Fig. 217, c, the line joining the mouth and anus Fig. 217. marks the axis of elliptical symmetry in the Urchin there figured (Galerites). The sexes are distinct in the Echinoderms, and the ovaries and testes are disposed in rays, opening in the Sea Urchins, by oviducts or sperm ducts, placed symmetrically round the anus, and equal in number to the typical number of rays. The Echinoderms are divided into the following Orders : a. The Crinoids Sea Lilies. b. The Asteroids Sea Stars. c. The Echinoids Sea Urchins. d. The Holothuroids Sea CucumhiTs. (a.} The Crinoids, or Sea Lilies, have a calcareous integument, or external skeleton, formed of symmetrical plates; with jointed rays, or tentacles surrounding the mouth, which is always superior. This whole Family belongs rather to the former period of the history of our globe than to the present, Most of the fossil Crinoids were attached to the sea bottom, by means of a flexible, jointed column (Fig. 218) (Apiocri- nus) ; and others lay at the bottom, without being attached (Fig. 219) (Saccocoma) ; and it is remarkable that the fixed forms occur earliest in Geological history. There are two living forms of Crinoids, Pentacrinus and Comatula, of which the first is fixed, and the second is iree ; but it was ascer- CRINOIDS. 375 Fig. 219. tained by Mr. Thompson, that in its earlier stages, Comatula is fixed like Pentacrinus to the solid rock ; thus the history of the developement of the Crinoids on the globe follows the order of developement of the individual. (5.) The Asteroids, or Sea Stars have a depressed, free body, multangular or radiate, with a leathery or calcareous integument ; mouth central, inferior. The Asteroids are divided into Ophiurids, or Brittle Stars, and Asterids ; the Ophiurids have arms distinct from the disk (Fig. 220). The Asterids have the arms confounded with the disk (Fig. 216), and are generally fur- g. 218. Fig. 220. nished with a madreporiform tubercle on the dorsal sur- face, surrounded by a row of calcareous nipples. In most of the Asterids five arms occur, which is regarded as the typical number ; but there are species in which rays from four to thirty are met with. The Asterids are very vora- cious, and act as sea scavengers ; they glide rapidly from place to place, by means of their ambulacral feet, and feed principally on Mollusks, which they are said to paralyse by means of the juices of their everted stomachs. 376 ELEMENTS OF NATURAL HISTORY. (c.) The EcMnoids, or Sea Eggs. Body subglobose, or depressed, without radiant lobes ; mouth and anus distinct, and mouth inferior ; integument calca- reous, beset with moveable spines. The plates of the Echinus (Fig. 221) are either pentagonal or hexagonal, and are arranged in a series often zones or lunes, five of which, commonly narrower than the others, have two rows of am- bulacral pores, through which the feet are protruded, as al- ready described. Around the anus are placed five apertures (sometimes only four), which are the outlets of the oviducts or sperm ducts ; and these outlets are situated in as many calcareous plates, of which one, larger than the rest, cor- responds to the madreporiform tubercle of the Sea Stars, and gives admission to the water supply of the ambulacral sys- tem. The moveable spines, whose number increases with age, work by a ball and socket joint on tubercles placed in meridian rows upon the surface of the shell. The mouth of the Sea Urchins is furnished with five teeth meeting in a point, which grow continually from behind, like the teeth of the Rodents ; these teeth are worked by an apparatus of forty distinct muscles, and by means of them the animal nibbles at and swallows its food. They were first noticed by Aristotle, and are called by Naturalists Aristotle's Lan- tern, quite erroneously, for it was the entire shell of the Sea Urchin that Aristotle compared to a lantern, and not its mas- ticating apparatus. He says, " the Echinus is not continuous as to its surface, but is like a lantern without a skin stretched over it," alluding apparently to the pin holes for the ambulacral feet, which are easily seen in the empty shell, because they admit the light. ECHINOIDS. 377 (<) The Holothuroids, or Sea Cucumbers, have a free, cylindri- cal body, covered by a leathery skin, secreting occasional calcareous particles; mouth surrounded with retractile ten- tacles ; anus terminal, opposite to the mouth. In the most typical of these soft-bodied Echinoderms, the analogy to the other Echinoderms is remarkably shown by the pentagonal section of the cylindrical body, and by five longitudinal rows of ambulacral feet; in others, as in Holothuria (Fig. 222), the suckers are scattered either in rows or irregularly over the body, and the radiate structure almost lost, but "^|^21^8^Ssi^ still shown in the twenty radiating tentacles that Fig. 222. surround the mouth. The Siphon worms (Fig. 193) are placed by many naturalists among the Echinoderms, and evidently form a link between this group and that of the ringed worms ; the analogies of the Echinoderms and Scolecid worms are so numerous that Huxley has proposed to unite them together with the ringed worms into one province, distinct from the arthropod articulates, and to be called Annuloida. B. Ccelenterates. The Ccelenterate Radiates are so named from their want of a perivisceral cavity, distinct from the digestive canal and its processes (/eotXeVre^a). They are composed essen- tially of an outer and an inner layer, or integument, both of which are furnished with vibratile cilia. Many of them, also, possess the property of secreting peculiar threads, which produce stinging effects on the animals in contact with them. They have mostly tentacles placed round the mouth, with which they seize their prey; and in a few of the more highly organised, traces of nervous system are said to occur. In some the sexes are distinct, while others produce ova and sperm, and are capable 37* ELEMENTS OF NATURAL HISTORY- also of reproduction by budding. With the exception of t\vo freshwater genera, all the Ccelenterates are marine. They may be conveniently divided into two classes a. Actinozoans. b. Hydrozoans. (a.) The Actinozoan Radiates are Coelenterate animals, in which the inverted wall of the general digestive sack is separated from the general wall of the body by a wide space, subdivided into chambers by a series of vertical partition, on the faces of which the ovaries, or sperm cells, are developed (Fig. 225). To the Ac- tinozoa belong, among others, the Sea Anemones (Fig. 223), and Coral Polyps (Fig. 224), which differ only, as the shelly Gasteropods and Slugs differ, by the faculty of secreting car- bonate of lime, which the Coral polyps do internally, as the shelly Gasteropods do externally. The Sea Anemone (Fig. 223), may be regarded as the type of Fig. 223. Fig. 224. the Actinozoans ; it is of a soft, leathery consistence, and attaches itself by its base to the rock, its mouth being placed opposite to the base, and facing the sea water, which furnishes it with food. Numerous tentacles, arranged after Nature's fashion, alternately in concentric circles, surround the outer margin of the voracious mouth, which readily swallows whatever soft edible substance is placed within its reach ; and these tentacles, with their thread cells, are even capable of seizing and of paralysing an animal as ACTINOZOANS. 379 highly organised as a Tadpole that unhappily strays inside their magic circle. The mouth in the Sea Anemone is not circular, but elliptical, the major axis of the ellipse being well marked by a white diameter, or ray, that crosses the disk, and forms one of the prominent body walls of the animal. This remarkable dia- meter declares the elliptical symmetry of the Actinozoan, and shows its relationship to the Echinoderms, the highest form of Radiate animals. A transverse vertical, or meridional section of a Sea Anemone, exhibits the structure shown in diagram 225; here we observe two concentric tubes, the outer being formed by the body wall, and the inner formed by the boundary of the digestive sack. The annular space be- tween these cylinders is divided by a number of radiating partitions, arising at definite intervals, from the inner surface of the body wall. Some of these radiating par- titions unite completely the body wall and stomach wall, and act as mechanical supports to both; while others of the partitions traverse only a portion of the distance between these concentric tubes ; to these imperfect partitions, which are always of more recent growth than the primary or perfect radiating partitions, are generally attached the ovaries, or testes, of the Sea Ane- mone. The Coral Pulyp differs from the Sea Anemone only by the property of depositing or secreting a calcareous skeleton in its ra- diating partitions, and body and stomach walls ; the skeleton thus secreted (Fig. 2 24), survives the soft part of the Coelente- rate animal that produced it, and thus remains as a coral, em- bedded in the rock, for the study of future geologists. In this manner naturalists have been enabled to compare to- gether the Actinozoans with calcareous skeletons belonging to all epochs of the history of the globe. 380 ELEMENTS OF NATURAL HISTORY. The Actinozoans are divided into the following Orders : 1. Zoantharia. 2. Alcyonaria. 3. Rugosa. 4. Ctenophora. The Zoantharian Actinozoans comprise the Sea Anemones and Corals already described, many of the latter being composite in character, and consisting of numerous individuals forming one Polypidom, as shown in Fig. 226. Each indivi- dual Zoanth has the true structure of the Acti- nozoan, and contributes to the general welfare of the community the products of digestion of any prey it is lucky enough to capture. They consti- tute a true Republic, in which each citizen, whether consciously or not, is compelled to sup- port the general state, by which he himself exists. In the Zoanths, the tentacles and radiating partitions are disposed in multiples of the number six, and, more rarely, of the number five. The Alcyonarian Actinozoans contain the Sea Pens (Fig. 227), the Organ pipe Co- rals, and the Gorgonias; they are charac- terised, like the Rugose Corals, which are exclusively fossil, by having their tentacles and radiating partitions multiples of the number four, instead of the numbers five or six, which prevail in the Zoanths. The Ctenophore Actinozoans have, as their name implies, comb-shaped meridional lines drawn upon their globular, or sub- globular bodies (Fig. 228 a, ft). They are transparent, often luminous, oceanic deli- Fig. 227. cate Actinozoans, and swim by means of the cilia attached to their Fig. 226. A CTINOZOANS. 3 8 I meridional fringes. In Fig. 228, a, is represented the Beroe, one of the best known of the luminous Actinozoa, found in countless Fig. 228. myriads in the Northern Seas, where it forms the food of nume- rous Cetaceans and other animals. These Ctenophores present numerous variations of forms, but are all comprised within the anatomical limits that define the Actinozoans, and distinguish them from the Hydrozoan Radiates. (i.) The Hydrozoan Radiates are Ccelenterate animals, in which the digestive sack and body cavity form one continuous cavity ; and the reproductive organs are external. A diagrammatic view of this structure is given in Fig. 229, which represents the ideal Hydrozoan, just as Fig. 225 represents the ideal Actinozoan. The body of the Hydrozoan, like that of the Ac- tinozoan, is formed of an outer and an inner membrane, or integument, the tentacles being composed of prolongations of both. Thread Cells are developed in the Hydrozoan from the inner layer, and possess the same properties as in the Actinozoan, only in a less marked degree. They are as voracious Fig. 229. as the Actinozoans ; and, like these, are either unisexual or hermaphrodite. ELEMENTS OF NATURAL HISTORY. The Hydrozoans are divided by naturalists into the following groups : 1. The Hydridae. 2. The Corynidae. 3. The Sertularidae. 4. The Calyciphoridae. 5. The Physophoridae. 6. The Medusidae. 7. The Lucernaridae. The Hydridce include the freshwater Hydra (Fig. 230), which first attracted the at- tention of naturalists to the peculiarities of the Hydro- zoans. The Hydra consists of a long tube, enclosing the sto- mach, and terminated by a mouth surrounded by seven tentacles ; and its ordinary mode of reproduction is by budding, as shown in the figure ; when removed from the water, the Hydras appear as minute specks of jelly, but quickly re- iii cover their true form on being again immersed in the water; Fig. 230. they feed voraciously, and seem to possess the power of benumb- ing their victims by means of thread cells, like the Actinozoans. The Sertularida; are Hydrozoans, composite in their charac- ter, like the Polyzoan Mollusks, but, of course, much less complex in their anatomical structure. They are well known to seaweed collectors, and are often confounded with the Polyzoans. One of the best known of our native forms is shown magnified in Fig. 231. Each of -the minute cells in this Sertularian protects a distinct Polyp, having the simple structure of the Hydra, and the HYDROZ04NS, 383 food it consumes is digested, not only for its own benefit, but also for that of the whole community. Of the seven divisions of Hydro - zoans, the Hydridce and Sertidarida just noticed, and also the Corynidte (Club Hydras), and Lucernaridte (Lantern Hydras), are sessile ; while the remaining groups, the Medusida, the Calyciphorida, and the Physo- phorida, are free swimmers, and oceanic in their habits. Of these, the best known are the Medusida, illus- trated in Fig. 232. These beautiful animals, well known as Sea Nettles, from their stingingproperties, abound in almost every sea, and sometimes attain a very considerable size. The Medusa, or Sea Nettle, or Sea Blubber, consists essen- tially of an inverted hemisphere, or swimming calyx, from the cen- tre of the under surface of which the digestive sack is suspended with its mouth downwards. The Swimming Calyx is provided with a complicated system of canals, and varies considerably in form among the different species of Medusida. 6. Protozoans The Proto- zoans are the lowest forms of animal life, and are properly ex- eluded from the Radiates, which they resemble in no feature of their structure. They may be defined by negative rather than by positive qualities. In none of the Protozoans have a nervous system and organs of sense been 2 3 2 - 384 ELEMENTS OF NATURAL HISTORY. discovered, and in many of them the existence of a digestive ap- paratus has yet to be ascertained. Most of the Protozoans are reproduced by vegetative budding, and they are essentially aquatic in their habits, and none of them, except the Sponges, attain an appreciable size. The Protozoans are divided by Naturalists into the following groups : A. Rhizopods. B. Sponges. C. Gregarines. D. Infusories. A. Rhizopods The Rhizopods are so named from the faculty they all possess of shooting out, apparently at will, long slender processes called pseudopodia, from, various parts of the soft, gelati- nous, uniform mass of which they are composed. These pseudo-- podia are shown in Fig. 233, which represents one of the common- Fig. 233- est forms of these Protozoans (Amoeba). The Amoeba extends its pseudopodia around any small digestible substance with which it comes in contact, and absorbs nutriment from it by simple im- bibition, or endosmose, like the rootlet of a plant. The Rhizopod, figured at Fig. 233, is composed altogether of PROTOZOANS. 385 soft parts, and possesses no definite shape ; many of the Rhizopods, however, secrete highly symmetrical skeletons, either of carbo- nate of lime, or of silica, and are well known to Geologists from their abundance in certain strata. These Rhizopods are called Foraminifers and Polycystines, and are found in great numbers, forming the floor of the ocean in deep seas. The Foraminifers, Fig. 234, are usually covered by a calca- reous shell, consisting of an aggregation of small cells com- municating with each other by means of minute apertures. - During life, all these cells and their communicating canals are ~ filled by the uniform pulpy mass of the Rhizopod, which protrudes its hair-like processes externally, exactly in the same manner as the soft-bodied Rhi- zopods. Most of the recent Fora- minifers are microscopical in size, while many of the fossil forms attained considerable dimensions. The Polycystine Rhizopods are smaller than the Foraminifers, and differ from them in secreting a siliceous instead of a calca - reous skeleton. Their shells are remarkable for the exquisite beauty of their forms. B. Sponges. The Sponges were recognised by Aristotle as true animals, and as possessed of sensation, although they resembled plants in some respects. They are well known by their skeletons, which are composed of fibres of a horny texture, strengthened by needles, orspicula, of siliceous or calcareous matter ; and this frame- work is so connected together, as to form a kind of fibrous skeleton. During life, the skeleton or sponge is coated by a gelatinous, ho- mogeneous, substance, like that forming the mass of the living Rhizopods, and furnished with cilia, which, by their incessant 2 c 3 86 ELEMENTS OF NATURAL HISTORY. vibratile movements, cause a continual circulation of water through the canals that traverse the substance of the Sponge. On examining a Sponge, it will be seen that these canals (Fig. 235) communicate with the external water, directly or indirectly, by many minute, and a few larger openings. The water circulation in Fig- 235- the Sponge is effected by the influx of water through the smaller openings, and by its efflux through the larger apertures. The cilia of the sponge are not arranged uniformly along the walls of the canals, but occupy definite positions in small spherical cells at in- tervals, marked c, c, c, c, in Fig. 235. These vibratile centres may be regarded as the individuals that compose the complex sponge, which has been compared by Huxley to " a kind of subaqueous city, where the people are arranged about the streets and roads, in such a manner that each can easily appropriate his food from the water as it passes along." C. Gregarines. The Gregarines are considered by naturalists as the simplest in structure of all animals. They occur as Ento- zoans in the Articulates, such as Cockroaches and Earth worms ; and are utterly destitute of either mouth or intestines, living alto- gether by the imbibition of the juices that surround them. They consist essentially of a delicate elongated sack, filled with a homo- geneous granular jelly, or sarcode, and enclosing a small, and more solid nucleus. Less is known of these obscure beings than of any other animals. SPONGES. 387 D. Infusories. The Infusories are microscopic animals, much smaller than the Rotifers, and constituting for the most part the food of the latter ; they swim about by means of cilia covering the surface of their bodies ; and have been proved to possess an organi- sation considerably in advance of that of Rhizopods, Sponges, or Gregarines ; forthey are found to contain both a mouth and an anus opening near it. The mouth leads into a gullet, open at the bottom, and not leading into a stomach or intestinal tube, but losing itself in the soft central mass of sarcode that constitutes the main body of the Protozoan ; in like manner, the anus commences vaguely in the same soft sarcode, and drains it, without the aid of a regular intestinal tube, of its excretory products. It has been also ascertained that these microscopic Infusories are hermaphrodite, each individual producing both ova and sperm cells, by contact of which a true generation is effected, in no essential respect dif- fering from what occurs among the higher animals. THE END. 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