UNIVERSITY OF CALIFORNIA AT LOS ANGELES CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY By N.'A. fcOBB 914 - 1935 CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY Contents Page I. Antarctic Marine Free-Living Nematodes of the Shackleton Expedition 1 II. North American Free-Living Fresh-Water Nema- todes Z5 III. The Asymmetry of the Nematode Bunonema in- equale, n. sp 101 IV. Selachinema, a New Nematode Genus with Remark- able Mandibles 113 V. Notes on Nemas 117 VI. The Mononchs, a Genus of Free-Living Predatory Nematodes 129 VII. Filter-Bed Nemas: Nematodes of the Slow Sand Filter-Beds of American Cities 189 VIII. The Orders and Classes of Nemas 213 IX. One Hundred New Nemas (Type Species of 100 New Genera) 217 X. Howardula benigna, a Nemic Parasite of the Cucumber -Bee tie 345 XI. Marionella ' 353 XII. Greeffiella 359 XIII. An Amendation of Hoplolaimus Daday 1905 nee auctores 363 XIV. Notes on Paratylenchus, a Genus of Nemas . . . 367 XV. Biological Relationships of the Mathematical Series 1, 2, 4, etc 371 XVI. Nemic Spermatogenesis 375 XVII. The Screw Nemas, Parasites of Codfish, Haddock and Other Fishes 388 XVIII. Ungella secta n. gen. n. sp., a Nemic Parasite of the Burmese Oligochaete (Earthworm) .... 394 XIX. A New Species of the Nemic Genus Syringolaimus. 398 XX. The Chromatropism of Mermis subnigrescens . . . 403 XXI. Survey of Nemas in Marine Beach Sand 411 XXII. The Ambulatory Tubes and Other Features of the Nema Draconema cephalatum 413 XXIII. Observations on the Morphology and Physiology of Nemas 419 XXIV. The Demanian Vessels in Nemas of the Genus Oncholaimus 423 XXV. Metoncholaimus pristiurus (Zur Strassen). . . . 439 XXVI. A Key to the Genera of Free-Living Nemas . . . 451 87184 ANTARCTIC MARINE FREE-LIVING NEMATODES OF THE SHACKLETON EXPEDITION Contributions to a Science of Nematology I BY N. A. COBB (With fifty illustrations in the text) BALTIMORE WILLIAMS & WILKINS CO. 1914 To Shackleton And his Men, Who to bring these stranger forms Braved the ice and cold Of the Southern Main, This tribute from a comber of milder shores. ANTARCTIC MARINE FREE-LIVIXG NEMATODES OF THE SHACKLETON EXPEDITION BY N. A. COBB CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY l Nematodes are so frequent in the Shackleton collections as to prove the seabottoms of the farthest south to swarm with these little beings. Hundreds of them, male, female and young, were taken from a mere thimbleful of the dredgings. The same tale comes from stations wide apart. Countless myriads find sustenance in these cold dark depths, and must in their turn be devoured by larger forms, until the series culminates in herds of seal and schools of whale. "All that in them is," takes on added meaning! Whence do these nematodes derive their sustenance? The stomachs of a number of the species contain diatoms with such regularity as to leave no doubt that these microscopic plants constitute a main food supply. The undigested frustules of the diatoms are voided and go to make up the permanent sea floor, so that the interesting little creatures whose portraits follow, or at least a part of them, assist in building what some future epoch may disclose as dry land formations of diato- maceous earth as remarkable as those of the United States or those of Tripoli. Some of the other species appear to be predacious, though none belong to the truly carnivorous group of the Enoplidae. No doubt the greater part of the species are vegetarian. These antarctic species are on the whole somewhat smaller than those of warmer seas, but one of them, that mentioned last, is a veritable 1 N ematology a contraction of Nematodology. The founding of this branch of science, on a par with Entomology for example, is fully justified by the fact that the Nematodes constitute such a distinct and highly characteristic group of organisms, containing an enormous number of species readily susceptible of division into definite Orders, some of which are of great economic importance. ANTARCTIC MARINE giant of its kind. Seven tropical Monhysteras taken at random from the writer's collections prove to average hardly 50 per cent longer than the average of the seven polar Monhysteras here described. There is little evidence that these polar species are less fecund than those found elsewhere. It is hardly conceivable that the body tem- perature of the marine polar species is higher than that of the water in which they live, namely, near the freezing point of fresh water, and yet, in spite of the freezing temperature, and the long polar night, nematode protoplasm seems to glide on through its mitosis dance to much the same purpose as if bathed in equatorial light and ensconced in the warm pools of tropical reefs. Through long residence and much travel in Pacific regions the writer has had unusual opportunity to become acquainted with their charac- teristics, and having at times paid particular attention to the marine nematodes of these re- gions (map), is able from personal observa- tion to say concerning the nematodes Lieu- tenant Shackleton's expedition brought from the far South, that in nothing are they more remarkable than in the striking resem- blance they bear to forms found in the warmer parts of the water hemisphere. Their nearest known relatives are found in Xew Zealand and the islands off the coast of the south end of South America. Nearly all of the Shackleton species belong to known genera, and the two new genera are nearly related to genera already known, Aplectus to the known Plectus and Austronema to the known Monhystera. Fig. 1. Marks indicate about twenty of the author's Xematode Stations Xorth American, Asi- atic, Australasian and Oceanic at the great ma- jority of which he has made personal examinations, and with the nematode fauna of which the Shackle- ton nematode collections are compared. FREE-LIVING NEMATODES 5 The spermatogenesis of Terschellingia polaris, n. sp. presents some very interesting features which are noted in connection with the de- scription. Kecently it has been suggested that of the two kinds of spermatozoa Boveri and Schleip have shown to exist in the males of the free-living generation of Khabdias bufonis, 2 one kind, supposedly that producing males, becomes functionless, thus accounting for the succeeding generation consisting solely of "parthenogenetic females," found in frogs' lungs. The spermatozoa of Ascaris equorum 3 and (?) Cystidicola farionis f have been shown also to be of two sorts. In all these cases the two kinds of spermatozoa are very similar to each other, so much so that the differences were long overlooked by keen observers. In Terschellingia polaris the differences in the male generative cells are of an extremely striking character, and seem to lend countenance to the earlier suggestion of the writer, that spermatocytes may in their reduction division produce polar bodies or their true homologues, abor- tive spermatozoa. We realize now that there has been too large a degree of assumption in taking it for granted that all four of the sper- matozoa quartette are equivalent simply because they are similar in form and size. A careful examination of their structure is revealing important differences. Very possibly it is a comparatively minor phenomenon that the polar bodies of eggs remain attached to their larger functional companion cell. Taking this view, three of the four companion-spermatozoa may, without violence, be regarded as homologues of the "polar bodies." Whether they are functional or not is a matter that may be considered quite apart from their history or structure. Generally speaking we know little or nothing about their relative "potency." That all, or any definite fraction of them are functional is more or less pure supposition. What we know is that some of them are functional perhaps all, per- haps not. Though these things are thus far outside our field of experience, they constitute problems that seem certain soon to be attacked from the experimental side, by following the history of specific members of the spermatid quartette; and one object of this note is to call attention to the fact that the free-living nematodes offer an attractive field for such work. 2 Rhabdias bufonis (Schrank 1788) S. and H. 1905 = " Rhabditis nigrovenosa." 3 A scan's equorum Goeze 1782 = "A scan's megalocephala." 4 (?) Cystidicola farionis Fischer 1798 = " A ncry acanthus cystidicola." 6 ANTARCTIC MARINE Incidentally there is raised the very interesting question whether Terschellingia polaris may not be the free-living form of a dimorphic species having a parasitic stage in some higher antarctic form. It is the writer's impression, based on a very considerable amount of obser- vation, that numerous free-living nematode forms, marine as well as land and fresh water, belong to such dimorphic species. The following diagram illustrates the nature of the formula used in the tabulation of the various necessary measurements : Fig. 2. Diagram of the descriptive decimal formula used for nematodes ; 6, 7, 8, 10, 6 are the transverse measurements, while 7, 14, 28, 50, 88 are the correspond- ing longitudinal measurements. The formula in this case is : 7. 14. 28. 50. 88. T! 8. 10. 6. The unit of measurement is the hundredth part of the length of the body, whatever that may be. The measurements become, therefore, percentages of the length. The absolute length is given in millimeters as a final non-paired term. The measurements are taken with the animal viewed in profile; the first are taken at the base of the pharynx, the second at the nerve-ring, the third at the cardiac constriction or end of the neck, the fourth at the vulva in females and at the middle (3/) in males, the fifth at the anus. The formulae represent the average of several specimens. When the specimens were received from Mr. James Murray, the biologist of the Shackleton Expedition, they were in formalin. They were next treated with cold concentrated solution of mercuric chloride, then stained with Mayer's acid carmine and finally examined in balsam. It is W 7 ell to bear these facts in mind in reading the measurements, as both the relative and absolute measurements vary somewhat with various methods of fixation and preservation. The number of speci- mens and their state of preservation is noted at the end of each de- scription, and from the data a rough guess may often be made as to the abundance of the species and the relative frequency of the sexes. By the use of suggestive conventional signs the formulae are made to convey considerable additional information. Thus the formula on p. 7 indicates that the cuticle is traversed by rather coarse transverse striae, 5 * Formula line of short dashes. See table, p. 7. FREE-LIVING NEMATODES 85. ~ 2 . -H T.T which are resolvable into rows of dot-like markings 6 modified on the lat- eral fields, 7 where there are distinct wings to the cuticle, 8 one on each side of the lateral lines. The N \ excretory pore is located near the lips, 9 and the tail end is armed with ph iii! i sp caudal glands and a spin- neret. 10 The oesophagus has a posterior or cardiac bulb two-thirds as wide as the base of the neck. 11 The two ovaries are symmetrically ar- ranged, reflexed, and occupy 19 per cent of the length of the body. 12 And, similarly, the male internal sexual organ is single and outstretched, and occupies 56 per cent of the length of the body. Among the dredgings at Ross Island were three containing nematodes which furnished material for this report. These three were marked: (1) "Bay, Cape Royds, in 10 to 20 fathoms of water, May 81, 1908;" (2) "Cape Royds, in 25 to 50 fathoms of water, July, 1908;" (3) "Bay, in 13 fathoms of water, April 30, 1908." These are referred to in the following descriptions as, (1), Bay, Cape Royds; (2), Cape Royds; and (3), Bay. Terminology relating to Striation of Cuticle. Tern 250 500 Bather fine 750 Fine " 1000 Very fine " 1500 or more None The camera lucida sketches are all made to the same scale, namely, a magnification of 750 diameters, except in the case of Thoracostoma, which was drawn at 400 diameters. The sketches may be relied upon as accurate. Information in the keys is not repeated elsewhere. 8 Dots above and below the line between the second and third terms. 7 Modified dots outside those just mentioned in 6. 8 Lines above and below the formula line between the second and third terms. 9 Oblique line near the pharyngeal terms of the formula. 10 Angular mark at right-hand end of formula. 11 Underscoring the third diametral measurement, thus indicating the presence of a bulb. Length of mark indicates the size of the bulb. 12 Curved marks before and after 47, and 19 used as an exponent figure. NOTE : Absence of any particular mark indicates the absence of that particu- lar feature so far as at present known. ANTARCTIC MARINE KEY BASS!) OH CHARACTERS NOT EMPHASISED ELSEKHEf 25 New Species and 2 New Genera -f- Terschellingia polaris 5 meridiana 14 edentata 16 Austronema spirurun 8 . -n- Monhystera .-F. -f Monhystera pilosa unifonais frigida TAIL CONOID, THEN CYLINDROID,AT LEAST IN FEMALES Posterior(cardiac)oesophageal bulb present "Bulb oblate :... Bulb pyrifora Musculature of bulb broken into 2 parts ; striae resolvable into elongate markings Wings (interrupted striae) inconspicuous 'f Chronadora Wings pronounced -n 'f Spilophora Musculature of bulb unbroken; striae resolve into dotlike markings, at least on head Striae difficult of resolution Spira septentrionalis 1 Striae easy to resolve Cardiac bulb three-fourths as wide as neck ._-':' Spilophora antarctica 17 Cardiac bulb one-half as wide as neck _--'f Aplectus antarcticus '3 Posterior(cardiac)oesophageal bulb none Anphids almost invisible transverse slits ::ia subsirailis -2 Anphids circular, usually 'easy to see Pharynx Plectoid, long, resembling oesophagus .. - Pharynx short, often small Intestinal cells clearly reticulated Sabateria antarctica 4 Intestinal cells not clearly reticulated Oesoph. trifle larger fn. behind nerveri Oesophagus plain Renette distinctly developed Somatic setae as long as body is wide Somatic setae none or inconspicuous . Renette inconspicuous or none Chromatin bodies, 1 in front of each anph'd-n -f Monhystera Chromatin bodies n'r.acphids none or faint Contour crenate.esp. vejitral side of tail ----f Monhystera Contour entire -f Monhys. septentrionalis TAIL CONOID, NO PART CYLINDROID Po3terior(cardiac)oesophageal bulb present Bulb elongated, not clearly subdivided; renette cell probably ellipsoidal -?.--:"- La xus septentrionalis Bulb pyriform, musculature broken into unequal parts; renette cell elongated Contour on ventral side of nale tail serrate .-?. 'f Spilophora Contour entire Benette cell 1/^wide as long ;Phar. bulb faint .-71 Chroiadora Renette cell ^ " " " " pronounced-:- 'f 1 Euchr. septentrionalis 19 Posterior bulb none!12,13), or a sere swelling Striae of minute BO re or less elongate elenents Dorsal tooth with no minute dental opponents .-;?. 'f Euchrorcad. antarctica 20 Dorsal " with 1 (22) or 2 (21) Subn. " " Tail regular, terminus about Vg wide as base . 'f' Euchronad. denticulata 21 Tarl suddenly narrowed on Vent. side n'r.anus -n 'f' Euchrosadora neridiana Striae appear impossible of further resolution Lips strong, chi tinous,acute,conoid,eversible . Axonolaimrs polaris Lips not acute, nobile but not eversible Cardiac region conspicuously non-staining n-f Monhystera meridiana Cardiac region of average nature Unicellular lateral glands and pores absent _-j Monnystera antarctica 13 Unicellular lateral glands and pores present---'!' Thoracosio-a polare 25 polaris 10 11 23 serrata 18 polaiis 15 22 . 2-1 12 FREE-LIVING NEMATODES KEY. BASED ON MALE CHARACTERS 19 New Species and 2 New Genera PRE-ANAL SUPPLEMENTARY ORGANS PRESENT Suppl. organs IQ.submedian, in 2 rows of 5 each . . -m-f Thoracostona polare 25 Supplementary organs in a single ventral row Organs 3(or 1 i n Anticoma ),f a i n t in Sp .serrata Fora tubular, 1/5 as wide as long Length 2 / bod y Diam.jjust in front of spicula, - Length % " " ;Ant.Org. 1 tail-L'gth.f rin.anus - Form companulate.very minute, deep as wide .... Organs 7,equidistant > faint in Sp.edentata Form cup-like, as deep as body'wall is thick Cardiac bulb present Cardiac bulb reduced to a faint swelling .. Form papilloid.row 3 body-widths long PRE-ANAL SUPPLEMENTARY ORGANS ABSENT Accessory pieces to spicula absent or faint Spicula suddenly hookshaped at proxinal end . Spicula of usual form, cephalated by expans Fora arcuate, proximae ventral to body axi Anticoma .subsiiilis 2 -m-f Aplectus antarcticus 3 -m 'f Spilophora serrata is -m Chromadora polaris 15 -n T Euchromad. antarctica 20 -n 'f Spilophora edentata ie -m-f Austroneraa spirurum Q Form somewhat L-shaped,Prox. dorsal to B'dy Accessory piece or pieces to spicula presen Apophysis to accessory piece bending backw rd Proximal ends of spicula not cephalated Proximal ends of spicula cephalated Cephalated by constriction Cephalated by more or less expansion Form more or less L-shaped Structure rather robust Structure frail Form nearly straight, or arcuate Spicula nearly straight Spicula arcuate L'gth 2V% times anal body diameter L'gth l 1 /^ - not very slender Apophysis to accessory pieces absent Spicula cephalated by contraction Spicula cephalated by expansion Cephalum set off by a constriction Cephalum not set off by a constriction -a t' Spilophora antarctica 17 -m-f Monhystera raeridiana 12 -n -f- Terschellingia polaris 5 -ra-f Monhystera antarctica 13 -a f Monhystera polaris 10 -n -f Monhystera frigida 9 -m- Monhystera pilosa 7 -m-f Monhystera uniforuis Q -m f- Laxus septentrionalis 23 -;- ':' Euchromadora meridiana 22 -H 'f 1 Euchr. septentrionalis 19 -m 'f Spilophora antarctica^ KEY TO SIGNS 'f', ovaries 2, symmetrical .reflexed. -^-.testes 2, one extending each way. -f-, " 2 " outstretched. - n , " 2, one only outstretched . -f , ovary 1 .outstretched forward, -n .testis 1, outstretched forward. Abbreviations Ib , lip or lipregion on , pnaryngeal tooth am , anphid Ic , locule of cuirasse pp , labial papillae ph , pharynx oe , oesophagus st , cephalic setae sp , spinneret ep , excretory pore pc , cordifora piece 10 ANTARCTIC MARINE DESCRIPTIONS OF THE SPECIES CHARACTERS COMMON TO ALL THE SPECIES Disregarding Thoracostoma, which is exceptional in the large size of the caudal glands, the possession of eye-spots, of distinct dermal pores and of oesophageal glands, and also in the possession of relatively very strong spicula with a compound framework, it may be said that the following characters are common to all the species here described: There is no median oesophageal bulb, and no pre-rectum. The tail is of approximately the same form in both sexes, and in all cases is sup- plied with a rather simple spinneret, and with caudal glands the lat- ter confined to the tail. The eggs, so far as known, are smooth and comparatively thin-shelled, and are deposited before segmentation begins. All known males have equal spicula of simple framework, and all are without bursa. There are no eye-spots. The cuticle is colorless, or nearly so, is without distinct pores, and is destitute of longitudinal striae except obscure indications in Spilophora serrata and Chromadora meridiana, where the secondary elements of the cuticle arrange them- selves also to a certain extent in longitudinal lines. The renette, when present, has its cell behind the cardiac constriction, except in Anticoma. Glands in the interior of the oesophagus have been seen only in Thoracostoma, and possibly, though these latter are of another character, in Monhystera frigida and polaris. The intestinal granules give rise to a tessellation only in Anticoma and Laxus. The spicula are arcuate, except in some Monhysteras; and cephalated except in Anticoma, Terschellingia and Euchromadora antarctica. There are no male papillae except in Anticoma and Monhystera antarctica. Male supplementary organs occur only in Anticoma, Chromodora polaris, Eu- chromadora antarctica, Aplectus, Thoracostoma, and in Spilophora ser- rata and edentata. The musculature of the oesophagus is fine except in Thoracostoma and Monhystera polaris, frigida and pilosa, though it is somewhat coarse in the bulb of Laxus. If the reader will add these characters to those given under each species heading, and will utilize in a similar way the common charac- ters given in the keys and generic descriptions, he will find himself in possession of a very detailed description of each species, covering a number of new and interesting anatomical features. FREE-LIVING NEMATODES U SPIRA, Bastian, 1865 13 1. Spira septentrionalis, n. sp. The striae, invisible except near the head are resolvable into rather irregular dots. The three lips are without papillae. The i 7.4 10.6 Y 92.3 neck is cylindroid posteriorly, s ' i"g ' "2 is j 7' 1-4nm ' convex-conoid anteriorly. The amphids, seen thus far only in dorso-ventral view, have a central elevation, probably appear- ing as a "fleck" in the surface view, and are about half as wide as the corresponding diameter of the head. The oesophagus is half as wide as the neck, and ends in a rather obscure bulb containing an in- distinct valve, two-thirds as wide as itself. No distinct cardia was seen. The intestine, separated from the oesophagus by a collum about half as wide as the neck, becomes at once three-fourths as wide as the body; it is but a few cells in girth, and the cells contain few or no granules. The rectum is conspicuous, the posterior lip of the anus prominently elevated. From the anus the tail tapers for two-thirds of its length, then becomes cylindroid to the swollen terminus, which is one-fifth as wide as the base. The caudal glands were not clearly seen, but are apparently arranged in a loose tandem in the anterior third of the tail! The female reproductive organs are probably double and reflexed. Habitat; remarks. Cape Royds. Described from a single somewhat shrunken specimen. ANTICOMA, Bastian, 1865 2. Anticoma subsimilis, n. sp. The thin cuticle is almost invisibly striated. On each lateral line there is a row of five somewhat curved cervical setae, r ' 26 si 8 each having a length equal to one- r- ' '' :.. i.5mm. fourth the corresponding width of the neck. These two rows begin at a distance from the anterior end equal to nearly three times the width of the head, and have a length equal to the corre- sponding diameter of the neck. The cuticle becomes thicker at the lips, which bear a circlet of six papillae. The oesophagus is cylindroid in the anterior part, but becomes conoid posteriorly. The mobility of the lips is proved by the nature of the ingested food. Seen dorso-ventrally the pharynx appears more nearly cylindroid than when seen laterally. Seen laterally it tapers so that finally it is one-fifth as wide as the corresponding part of the head. The lining is rather thin, but refractive. The cardia, one-half as wide as the neck, is conoid with a short cylindroid extension. The rather thick-walled in- testine, separated from the oesophagus by a collum three-fifths as wide as the neck, becomes at once three-fourths as wide as the body, and is about six cells in girth. The intestinal cells contain numerous small, uniform, distinct granules. The posterior lip of the anus is elevated. The caudal glands are packed together 13 The abbreviations used in lettering the sketches, which represent the ante- rior and posterior extremities respectively, are explained near the foot of page 9. As a rule the information given in the sketches is not repeated elsewhere. As far as possible the sketches are derived from typical specimens. 12 ANTARCTIC MARINE in the anterior two-fifths of the tail. The elongated renette-cell, two and one- half times as long as the body-diameter, and one-fourth as wide a? long, lies a little in front of the cardia, and is not re flexed. The excretory pore is somewhat behind the pharynx. Distinct nerve-cells, more numerous behind the ring, are arranged (at least in front of the ring), in six longitudinal groups. The cylin- drical part of the tail is about one-tenth as wide as the base. The slender, uniform, but rather strong spicula, as wide as the narrowest part of the tail, are twice as long as the anal body-diameter, and lie with their proxi- mal ends dorsal to the body axis. The proximal eighth of each spiculum is sep- arately more or less arcuate, so that one may speak of a curved cephalum or proximal end. Two separate accessory pieces, rather frail, bent at the distal end, one-sixth as long as the spicula and parallel to them, form a rather close collar round the distal ends of the spicula. On each side of the b'ody there are four equidistant, ventro-submedian, pre-anal, papilla-like setae, one-sixth as long as the body-diameter, extending in a row from near the anus to near the sup- plementary organ. There are about three ventro-submedian post-anal setae on each side of the middle part of the tail. Habitat; remarks. Cape Royds; Bay, Cape Royds. One adult and several immature somewhat shrunken specimens. This species differs from A. similis in having five pectoral hairs, longer setae, a sub-cyliridroid pharynx, and an oesophagus without expansion behind the nerve-ring APLECTUS, new genus Species of this newly proposed genus have the general form of Plectus, but have the phar3iix less definitely developed, and the renette-cell farther back and not reflexed. They differ also in having nearly obsolete lips, and a nearly cylindroid oesophagus whose small cardiac bulb is without a three-fold striated valve. The spinneret also differs from that of Plectus, as shown in the sketch. The male supplementary organs in the two genera also differ materially. These facts together with the marine habitat and the relative abundance of the males of Apleclus, appear to make necessary a separate genus for the reception of this antarctic species. The following is the type species. 3. Aplectus antarcticus, n.g., n. sp. The rather thin cuticle is traversed by about 700 duplex striae, which give the contour an obscurely doubly crenate appearance. Two wings, separated ! 12 : e - 2I> . . . '. 51 ' . . . 87 : , e,, b y a distance about equal to the width y^jj .8 2.2~^ 2.3, 2.4 1.9 ' O f an annule, begin near the middle ** -Q . : si of the neck and end near the middle H/ '....:. -r;r..: ' > .6mn. of the tail. Cervical setae, similar to the cephalic setae, occur one or two on each lateral line; and on the male tail there are setae, one-third to one-eighth as long as the body is wide. The lips are very small and difficult to observe. The pharynx, very inconspicuous and hard to distinguish, is probably double, the narrow, tubular, anterior part extending to a little behind the amphids, the pos- terior part, which closely resembles the oesophagus, extending nearly halfway to the nerve-ring where there is a break in the musculature. In the lateral view there are seen close behind the cephalic setae, under the cuticle, very minute FREE-LIVING NEMATODES 13 bodies that stain, of which those most clearly seen were the dorsal and ventral ones. Probably there is a circlet of these bodies. Just behind these stained bodies, that is, a little behind the setae, there is an appearance as if of a small quadrate cavity, one-third as wide as the head. This is not a cavity, however. Its posterior limits are a trifle more than a head-width from the anterior end. The amphids are variable in size and form,. being considerably larger and slightly more elongated in the male. The posterior border appears interrupted. The slender cylindroid oesophagus, is probably very obscurely Rhabditoid, and ends posteriorly in an obscurely rhomboidal to pyriform bulb or swelling, three-fifths to two-thirds as wide as the neck. The cylindroid cardia, one-fourth as wide as the body, and twice as long as wide, is really a modified part of the intestine, and is composed of small strongly staining cells. The thick walled intestine, sepa- rated from the oesophagus by a collum one-fourth to two-fifths as wide as the neck, is few, probably four, cells in girth. These cells contain numerous, indis- tinct, rather fine and uniform granules. The tail, tapering from the anus, is cylindroid in the posterior two-fifths and ends in an almost imperceptibly swollen apiculate terminus one-third to one-half as wide as the base. The caudal glands are arranged in loose tandem in the an- terior half of the tail; their ampullae are distinct and no wider than the ducts, but stain more strongly. The elongated renette-cell, which is difficult to observe, is as long as the body is wide, and one-fifth as wide as long, and occurs at a dis- tance behind the neck equal to eight times the width of the body. The very slender duct, invisible except where stained, empties through a pore apparently opposite the nerve-ring. The nerve-ring surrounds the oesophagus rather squarely and is accompanied by somewhat distinct nerve-cells rather definitely grouped. From the inconspicuous, small continuous vulva the small vagina leads inward halfway across the body to the straight uteri. The rather elongated eggs are two to two and one-half times as long as the body is wide, and fully one-third as wide as long. The broad ovaries, cylindroid, but tapering near the extremities, reach three-fourths of the way back to the vulva, and contain about twelve ova, ar- ranged rather irregularly. The spermatozoa in the uterus are of such a size that it would take at least seven or eight side by side to equal the body-diameter. The arcuate, rather strong, sub-slender, sub-acute spicula, one and one-fourth times as long as the anal body-diameter, are slightly cephalated by expansion, the cephalum being set off by a broad shallow constriction, and lie with their proximae dorsal to the body-axis. There are two rather strong, sub-slender, slightly bent accessory pieces, parallel to the spicula then bending away, the applied part being one-fourth as long as the spicula. The receding part is arcuate in the same direction as the spicula, and from its end there passes a strand of muscle to the ventral body-wall behind the anus. The ejaculatory duct is one- fourth, the vas deferens and cylindroid testes one-half as wide as the body. The blunt blind ends of the testes are two-thirds of the neck's length from the cardia and one and one-half times the tail's length from the anus, respectively. The protrudable, sub-equidistant supplementary organs are separated by a distance equal to nearly one and one-fourth times the body-diameter, and the posterior one is located at a distance in front of the anus equal to twice the anal body diameter. They are rather straight but have the distal third bent ven- trally, and the distal end flattened and pulled out posteriorly into a spur, or 14 ANTARCTIC MARINE toe, which always remains outside the body. The entire profile contour is like that of a high boot with its leg bent backward. The projecting part is twice as long as the diameter of the tube, and is roughened at the end with ten or twelve exceedingly minute striae or warts. The proximal ends of the organs are rounded and not cephalated. Habitat ; remarks. Bay, Cape Royds. About fourteen females and six males, in good condition. The sketch is that of a female. SABATIERTA, de Rouville, 1903 4. Sabatieria antarctica, n. sp. Striae about 800, resolvable with great dif- ficulty into dot-like markings. There are no lips. The tubular pharynx, ex- 9.3.17.7 Y as. tending to opposite, the posterior 2"."5 ' 2.6 zTs 2". 4 ' 9na ' borders of the amphids, as shown by a slight accentuation of the lining, is surrounded by an almost imperceptible, slightly unsym- metrical pharyngeal bulb three-fourths as wide as the head. At the somewhat oblique nerve-ring the oesophagus has a diameter equal to one-third the width of the corresponding part of the neck, but swells posteriorly to two-thirds the width of the base of the neck. The rather cylin- droid cardia is one-third as wide as the neck, and one and one-half times as long as wide. The thick-walled intestine, separated from the oesophagus by a collum two-thirds as wide as the body-diameter, soon becomes three-fourths as wide as the body and is about two cells in girth. From the elevated posterior lip of the anus the rather prominent rectum extends inward and forward a distance equal to the anal body-diameter. From the anus the tail tapers for three-fourths of its length, then becomes cylindroid to the slightly swollen terminus. The caudal glands are probably small and near the anus. Habitat; remarks. Cape Royds. Described from a single young specimen in fair condition. TERSCHELLINGIA, de Man, 1888 5. Terschellingia polaris, n. sp. The cuticle is traversed by about 700 striae, plainly visible near the extremities only. Narrow double wings, having a width about equal to that of two an- 33 nules of the cuticle, begin near ' : 8 . . . 9 : 9 : 15 : 5 .T 44 :. . . 84 : 9 , 73cra the middle of the neck. The _ : - 3.2 3.6 4. 2.5 central raised body, or "fleck," of the amphid stains about as strongly as the nuclei else- where in the body. Very minute, inconspicuous papillae, probably six in number, occur on the confluent lips. The vestibule is very minutely longitudinally stri- ated. About halfway to the amphids there is a break in the musculature of the oesophagus; the pharynx probably extends to this point. The conoid neck con- tains a cylindroid oesophagus which, near the nerve-ring, is one-third as wide as the neck, but ends in a bulb five-sixths as wide as the base of the neck. The lining of the oesophagus is distinct, its most prominent optical expression being a single refractive line. The cardiac valve causes a slight, simple modification in the lining, one-eighth as wide as the bulb. The more or less thick-walled in- FREE-LIVIXG XEMATODES 15 testine is separated from the oesophagus by a cardiac collum one-sixth as wide as the neck, and soon becomes two-thirds as wide as the body. The first few cells of the intestine, at the cardiac region, are very small, with relatively large nuclei that stain strongly. The intestine is separated from the rectum by a pyloric collum one-fourth as wide as the corresponding portion of the body. From the anus, whose posterior lip is elevated, the chitinized rectum leads in- ward and forward a distance equal to the length of the anal body-diameter. The granules of the intestinal cells are small and scarce. The tail tapers from the anus and ends in a slightly swollen terminus. A few small, stiff, cylindroid, blunt caudal setae are to be seen, mostly about one-fourth as long as the terminus is wide. The broadly saccate caudal glands, arranged in a loose tandem in the anterior fourth of the tail, empty through distinct ducts and elongated, narrow ampullae. What appears to.be an irregularly ellipsoidal renette-cell is located at a distance behind the neck equal to the width of the body; it is half as long as the body is wide, and three-fourths as wide as long. The nerve-ring, which surrounds the oesophagus more or less obliquely, is accompa- nied by distinct nerve-cells definitely grouped, both in front of it and behind, and extending backward to near the cardiac bulb. From the small and inconspicuous, but more or less elevated vulva, the conoid, non-chitinized vagina leads inward at right angles to the ventral surface two-fifths the way across the body. The eggs have a length nearly one and three-fourths times that of the body-diameter, appear about half as wide as long, and have been seen in the uterus one at a time. The medium sized, more or less tapering ovaries contain fifteen to twenty develop- ing ova, for the most part flattened and arranged single file. The more or less slender, sub-acute, uniform, slightly yellowish spicula have a simple and rather strong framework, and are one and one-fourth times as long as the anal body-diameter. The proximal ends appear to lie opposite the body axis. The triangular, blunt accessory pieces have a simple and rather frail frame- work; the part applied to the spicula is one-fourth as long as they, while the ta- pering apophyses lie a little backward and end opposite the body-axis. The ejac- ulatory duct is one-fourth, and the testis one-half, as wide as the body. The comparatively few (about a dozen) primary spermatocytes occur in the testis in single file, then come three pairs double file these latter relatively huge. That is to say, the primary soermatocytes increase much in size and then divide transversely into very unequal parts, a small distal part and a large proximal part, and these two unequal parts divide almost simultaneously in the longitudi- nal direction. Thus there appear four cells arranged in two pairs side by side, a small strongly staining pair with inconspicuous nuclei, and a large pair which do not stain except in their relatively small nuclei which show about seven small more or less globular chromosomes. These two divisions represent the usual reduction divisions, and give rise to spermatozoa of very different size and ap- pearance. The phenomenon is reminiscent of the formation of the polar bodies. In some specimens the smaller cells, those that in their appearance remind one of polar bodies, appear as if divided a second time, but there is uncertainty about this. It is the writer's intention to prepare a separate report on this species and its spermatogenesis. Habitat; remarks. Cape Royds; Bay, Cape Royds. Numerous specimens, mostly somewhat shrunken. 16 ANTARCTIC MARINE AUSTRONEMA, new genus The single species for which this new genus is proposed has many of the char- acters of Monhystera, but differs in so many important respects as to call for separate classification. The principal differences of generic value are the pos- session by Austronema of an oesophagus altered in the posterior half, a well developed ventral gland, special lateral cells, hamate spicula without acces- sory pieces, and glandular (?) organs associated with the spicula. Other minor differences exist, such as the occurrence of the special group of setae near the middle of the tail. The following is the type species. 6. Austronema spirurum, n. g., n. sp. The cuticle is traversed by exceedingly minute transverse striae. The lips are confluent. The conoid neck contains a cylindroid oesophagi!?, whose di- ameter measured near the nerve- J 4 ring is one-half as great as that of 87 3 the corresponding portion of the 2'; 2"* ' 8nn ' neck, but which finally becomes two-thirds as wide as the base of the neck. There is a break in the musculature of the oesophagus just behind the nerve-ring, and behind this break the refractive nature of the lining is some- what different, and, moreover, in many of the preserved specimens the diameter of the oesophagus from this point onward is suddenly somewhat greater. There is a conoid to cylindroid cardia about one-half as wide as the base of the neck. The very thick-walled intestine, two to four cells in girth, becomes at once three- fourths as wide as the body. For a short distance behind the cardiac collum, namely, for a distance about equal to two-thirds the body width, the tissues of the intestine do not stain. The lining of the intestine is refractive and distinct, so that the almost imperceptibly zigzagged lumen can be readilv followed. The intestine is separated from the oesophagus by a collum two-fifths as wide as tKe base of the neck. The size of the numerous, yellowish, uniform granules contained in the intestinal cells varies in the different parts of the intestine; they are much coarser posteriorly than anteriorly. From the anus, the posterior lip of which is elevated, the chitinized rectum extends inward and forward a distance equal to the anal body diameter. The tail tapers in such a manner that at the middle its diameter is about half as great as at the base. Its terminus is about one-fifth as wide as its base. The ellipsoidal caudal glands are arranged in a loose tandem in the anterior third of the tail. Very short, stiff, inconspicuous, ventrally submedian caudal setae occur on each side of the tail, two on the anterior half of the tail, and three near the middle and close together and finally, one or two on the cylindroid, narrow, posterior half. The pyriform to ellipsoidal granular renette-cell is located at a distance behind the base of the neck equal to one and one-half body-diameters. It is one and one-half times as long as the body is wide, and one-third as wide as long, and presses the intestine considerably to one side. It does not appear to have any companion cell. The medium sized nerve-ring surrounds the oesopha- gus somewhat squarely, and is accompanied by distinct nerve-cells extending well back toward the base of the neck. From the rather small, but rather con- FREE-LIVING NEMATODES 17 spicuous, elevated vulva, the well developed, tubular, muscular vagina extends inward and obliquely forward. It is about twice as long as the corresponding body-diameter, and about two-thirds as long as the uterus. The eggs are about as long as the body is wide, and three-fourths as wide as long, and have been seen two or three at a time in the uterus. The ovary is of medium size, and tapers so as to become narrow. It contains many ova, arranged single file somewhat irreg- ularly so near the uterus. The slender, more or less uniform spicula taper from the middle toward the proximal ends, and present the striking peculiarity of being strongly curved at the distal extremity, forming a hook across which there is a thin, transparent membrane. They are one and three-fourths times as long as the anal body-diam- eter, and are so arranged that their proximal ends appear as if lying to the dorsal side of the body axis. Their yellowish framework is rather strong, and the proxi- mal two-thirds may sometimes be seen to be nearly straight. At the extreme end the spicula have a very minute recurved apiculum or point. Two (?) pairs of ellipsoidal granular unicellular glands (?) occur some distance in front of the spicula. This species has the head of a Monhystera but differs, in having the oesophagus altered in the posterior half, a well developed ventral gland, special lateral cells, hamate spicula without accessory pieces, and the tail with a group of small setae near the middle. Habitat; remarks. Cape Royds. The five females and five males examined were in fair condition. MONHYSTERA, Bastian, 1865 The following are characters common to all the species of Monhystera here described. Cervical and somatic setae none or scattered and short, except in M. pilosa. Neck conoid, but cylindroid in the posterior half in M. pilosa, and M. meridiana. Tail tapering from the anus or a little in front of it. Oesophagus somewhat cylindroid without swellings of any kind, for the most part about half as wide as the nec'k, but finally three-fifths to three-fourths as wide as the base of the neck. Cardia present, except in M. frigida, hemispherical to cylindroid, and one-fourth to one- half as wide as the base of the neck. Intestine separated from the oesophagus by a collum one-third to one-half as wide as the neck, becoming almost at once about three-fourths as wide as the body, its walls thick and two to four cells in girth, and the lining usually so refractive that the lumen is a rather distinct feature. Granules of the intestinal cells numerous, fine and uniform. Rectum of about the same length as the anal body diameter. Caudal setae none or inconspicuous except in M. pilosa. Lateral fields one-third, more rarely one-half, as wide as the body. Renette unknown except in M. pilosa and M. uniformis. Nerve-ring of medium width, surrounding the oesophagus rather squarely, the nerve cells in its vicinity usually rather diffusely arranged. Vulva small or of medium size and in these species not very conspicuously elevated except in M. uniformis. Vagina one to two times as long as the body is wide, and extending inward and forward. 7. Monhystera pilosa, n. sp. Striae about 1700. There are numerous long, very slender, flexible cervical and somatic setae, often arranged in pairs, one member of IS ANTARCTIC MARINE the pair in front of the other, on the sub-median lines. There are probably three lips, bearing six minute setose papillae ar- ranged in a sin- gle circlet. The lining of the oe- sophagus is very ' distinct, and the musculature rather coarse. The granules of the intestine are yellowish brown. Toward the posterior extremity, for some distance in front of the anus, there is a strong development of lateral cells, which do not appear to exist elsewhere in the body. These cells extend forward toward the middle of the body, and have been traced no farther. Their size, which is variable, is such that two or three occur side by side in the lateral fields. The tail is cylindroid in its posterior three- fifths, with a width there one-eighth as great as that of its base, and has a slightly swollen terminus. The caudal ducts, of which two were seen, are narrow and distinct. From the excretory pore at the end of the third fifth of the neck there leads inward a very narrow duct whose length is nearly equal to the thick- ness of the cuticle. The duct leading thence back to the renette cell is, however, of considerable width about one-fourth as wide as the oesophagus and is read- ily traced back to a point opposite the anterior part of the intestine, where the renette cell pushes the intestine to one side. The spicula are uniform, with a width near the distal extremity one-sixth as great as the corresponding body width. The single accessory piece, parallel to and close to the distal thirds of the spicula, has an apophysis tapering to an obscure and slightly recurved point. This apophysis lies at right angles to the spicula, and then curves forward a little. The ejaculatory duct is one-third as wide as the body, the vas deferens considerably wider. The blind end of the anterior, larger testis is disposed in one or two coils. Habitat; remarks. Bay, Cape Royds. The single specimen examined was in good condition. 8. Monhystera uniformis, n. sp. Apparently there are three very obscure con- fluent lips. The amphids when seen in the dorso- ventral view seem to be well chitinized, and appear deepest in the anterior part, where they are one fifth as deep as the head is wide. The cardia is twice as long as wide. The cylindroid part of the tail is one-third to one-fourth as wide as the base. Broadly saccate caudal glands are found in the anterior half of the tail. At a distance behind the neck equal to three to four body-widths there is an ellipsodial renette cell with a large nucleus. This gland-cell is one and one-half times as long as the body is wide and half as wide as long. The location of the excretory pore has not been made out with certainty; 13.2 20. -83' .9 12.8 20. -M FREE-LIVING NEMATODES 19 possibly it is just behind the nerve-ring. The small, weak, tubular, non-chitinized vagina leads into a uterus which is five times as long as the body is wide. The eggs are about four times as long as the body is wide, and one-fifth as wide as long. The medium sized cylindroid ovary contains about twenty-five ova, arranged somewhat irregularly. The tail of the male is like that of his mate except that it is conoid nearly to the terminus. The very slender uniform spicula are two and one-half times as long as the anal body diameter. Their frame- work is simple, and the proximal ends lie somewhat dorsal to the body axis. The single accessory piece is frail, its framework simple; the applied part being one eighth as long as the spicula, the blunt, backward pointing apophysis being one- fifth as long as the anal body diameter and having its proximal end opposite the body axis. The ejaculatory duct is one-third, the testis two thirds, as wide as the body. Habitat; remarks. Cape Royds. Six females and three males, in fairly good condition. 9. Monhystera f rigida, n. sp. About 1400 striae give to the margin a crenate con- tour. The very inconspicuous lips are probably three in number. The amphids appear circular, but are really reg- < ^ , 36 ular spirals of one and one-half lb "~"/|P " 3 9 ' 7 18>1 ' B? winds, having a raised transverse ridge extending part way across. A deeply staining nucleus, of the same size and character as the nuclei of the nerve cells near the ring, occurs immediately in front of each amphid. In the posterior end of the oesophagus there are two, possibly three, elongated, granular gland-cells, quite as long as the body is wide. The rectum is prominent. The vagina is small and weak. The eggs are about four times as long as the body is wide. The rather narrow, cylindroid ovary contains twenty or more ova, arrang- ed mostly in single file. The uniform slender, frail, sub-acute spicula are one and one-half times as long as the anal body diameter and lie with their proximae op- posite the body axis. The very inconspicuous, very slender and frail acces- sory piece is bent so that the applied part is one-third to one-fourth as long as the spicula, while the uniform backward bending part is one-fifth as long as the anal body diameter. Its proximal end lies to the ventral side of the body axis. The ejaculatory duct is one-third, the testis two-thirds, as wide as the body. Habitat ; remarks. Cape Royds. The single female and the two males examined were in fair condition. 10. Monhystera polaris, n. sp. The 600 striae give to the margin a minutely crenate contour, most plainly to be seen just behind the anus. The three double, more or less distinct lips ^ j 4i are fairly developed. Two '-> i BO innervated papillae occur ! K5 2 ' 5 2 ' 6 3 ' 4 2>1 on each of the lips, six I i. 11. 21. -M- 84. papillae in all. The am- an w/?^-V'/,/ i.V^2.~5 2.V~ 2.V~ 2.7 Illma1 ' phids are sunken, but usually show a well stain- ed projecting margin two- thirds as wide as the amphid. A little in front of each amphid is a single some- what spherical nucleus, one-fourth as wide as the oesophagus, containing granules, 20 ANTARCTIC MARINE as do the ganglion cells near the nerve-ring. These two neuclei probably indicate the presence of two nerve cells. They are best seen in the dorso-ventral view. The refractive elements of the lining of the oesophagus, especially in certain aspects of the head, appear to extend into. the pharynx in a peculiar way, as shown in the sketch. The rectum is more or less prominent, and in the male the anus is raised. The tail tapers in such a manner that at the middle it is one-third as wide as at the anus. Its terminus is slightly swollen. Caudal setae appear on the base of the tail. The vagina extends inward nearly at right angles to the body wall, about half way across the body. The uterus, three to four times as long as the body is wide, contains spermatozoa one fifth as wide as the body. The posterior, rudimentary branch of the uterus, nearly twice, as long as the width of the body, also contains spermatozoa. The eggs are nearly twice as long as the body is wide, and one-third as wide as long. The broad tapering ovary contains about twenty ova arranged single file, and as many more packed irregularly in the distal fourth. The brownish, rather slender, uniform, acute spicula are one and one-third times as long as the anal body diameter. The framework of the spicula is more or less strong, and the proximal ends lie opposite or a little dorsal to the body axis. The single, rather straight and rather frail accessory piece is of a simple character, and has a backward pointing apophysis one-sixth as long as the anal body diame- ter. The male presents the peculiarity of possessing two testes, an uncommon thing in Monhystera. They are rather wide and of unequal size, the anterior, more or less cylindroid one being considerably the wider. The blind end of one testis is at the cardia, that of the other about one tail-length in front of the anus. Habitat; remarks. Cape Royds; Bay, Cape Royds; Bay. Seven females and six males, somewhat shrunken. The specimens from the various localities differ slightly in (1) the size and form of the cephalic setae, (2) the length and width of the spicula, (3) the prominence of the amphids, (4) the prominence of the striae on the tail. Diatoms and other unicellular organisms were seen in the intestine. 11. Monhystera septentrionalis, n. sp. The lips are confluent. The lining of the oesophagus is rather prominent, and one-fifth as wide as the oesophagus itself. 33 The small and inconspicuous, some- - u ' y ~ E6 83- .5mm. what ellipsoidal caudal glands are 1-9 arranged in a loose tandem in the anterior half of the tail. The anus is continuous. The conoid, rather muscular vagina is one and one-half times as long as the body diameter. The eggs are elongated, twice as long as the body is wide, and less than half as wide as long. About thirty ova occur in single file in the gently tapering ovary. Habitat; remarks. Bay, Cape Royds. Seven good female specimens. The amphids are often a little farther back than illustrated. 12. Monhystera meridiana, n. sp. The striae, about 1000 in number, are respon- sible for a somewhat crenate contour, more noticeable near the tail. The strongly developed cardiac region, set off by a constriction on each side, is as wide as the intestine, and forms a small but distinct segment of the alimentary canal. The vulva is elevated. Eggs twice as long as the body FREE-LIVING NEMATODES 21 is wide, and one-third as wide as long, occur in the straight uterus. Toward its blind end the narrow, tapering ovary is one-fourth as wide as the body. The tail of the male is conoid in such a fashion that at a distance from the anus equal to four times the anal body diameter it has a width equal to one-fourth the anal body width; thence it tapers very gradually to the terminus, whose width is con- siderably less than that of the spicula. The slender, uniform, acute spicula are one and three-fourths times as long as the anal body diameter. Theejaculatory duct and vas deferens are one-fourth as wide as the body. Apparently there are two tapering testes, but the end of the posterior one was not definitely seen; it appeared, however, to be eight to twelve body widths in front of the anus. Spermatocytes occur in single file near the end of the anterior testicle. Habitat; remarks. Bay, Cape Royds. One female and three males in a somewhat shrunken state. 13. Monhystera antarctica, n. sp. The cephalic setae are very minute and diffi- cult to see. Six excessively minute forward pointing papillae occur, one on each lip. Apparently the pharynx is tra- versed near its middle by a trans- verse ridge, and this is the reason I ^&\ !- 2 2.7 2.9 3.7 why it appears in optical section as if armed with two teeth. From the anus, the posterior lip of which is elevated, the rather prominent, chitinized rectum leads inward. Anal glands are present. The rather large and conspicuous nuclei of the intestinal cells are arranged about a body-width apart. The terminus of the tail is one-fourth as wide as the base. The broadly saccate caudal glands, of which two are larger than the third, are arranged in close tandem in the anterior half of the tail; their ampullae are distinct. The lateral fields are one-half as wide as the body. At a distance behind the base of the neck equal to four times the width of the body there is frequently to be seen in the female a large cell, one-half as wide as the body, with a prominent nucleus. This cell occurs in females only. Though its connections have not been definitely made out, it sometimes seems to empty through a pore a little in its rear. The straight uterus, five to six times as long as the body is wide, contains elongated eggs, as long as the bodj r diameter, and half as wide as long. The cylindroid ovary contains ova arranged in double file- irregularly so toward the blind end. The tail of the male is a little stouter than that of his mate. The rather frail, slender, uniform, sub-acute spicula, one and one-half to one and three-fourths times as long as the anal body-diameter, lie with their proximae dorsal to the body axis. The single accessory piece, parallel to the distal third of the spicula, and then bending back in a thumb-shaped apophysis, lies with its proximal end oppo- site the body axis. On the tail there are very faint inconspicuous setose papillae one ventro-submedian on each side, at the end of the anterior fourth, and two or three sub-ventral just behind the middle of the tail. The ejaculatory duct is one- fourth to one-third, the vas deferens and tapering testis one-half, as wide as the body. Habitat ; remarks. Bay, Cape Royds. Numerous slightly shrunken specimens. 22 ANTARCTIC MARINE CHROMADORA, Bastian, 1865 14. Chromadora meridiana, n. sp. Among the secondary elements into which the 600 transverse striae are resolvable there are two longitudinal rows that stand Ut al ^ the latfiral fields a '.6 8.8^13.8 '46 86. .V~3.~3 r r~3Y~5~~~?~2 > ' 9ia ' little more prominently than the others. Outside these, on on'' : : * B * either side, is another row almost imperceptibly emphasized. S P " "-"" The annules are retrorse posteriorly, and the reverse anteriorly, the change taking place opposite the vulva on the female. The few very short cervical and somatic setae to be seen scattered here and there are one-half to one- third as long as the body is wide, though a few nearer the head are considerably longer than the cephalic setae. There appear to be twelve subdistinct lips, each bearing a single papilla. The conoid neck contains a cylindroid oesophagus, which, measured at the nerve-ring, is one-third as wide as the corresponding portion of the neck. The oesophagus ends posteriorly in a bulb three-fourths as wide as the base of the neck, containing an inconspicuous elongated valve one- third as wide as itself. The musculature of the bulb is broken into two very unequal parts. There is no cardia. The wall of the intestine varies from thick to somewhat thin, and is six to eight cells in girth. The intestine becomes at once about three-fourths as wide as the body. Its lumen is distinct, and about one- fourth as wide as itself. The rather numerous granules to be seen in the cells of the intestines are uniform and small. From the anus, which is depressed, the chitinized rectum leads inward and forward a distance equal to the length of the anal body-diameter. The arcuate tail tapers from in front of the anus, but is usually cylindroid in the posterior fifth, and has a terminus one-sixth as wide as its base. The broadly sac- cate caudal glands are packed together in the anterior fourth of the tail, and empty through distinct narrow ducts. The length of the few, scattered, straight caudal setae is about equal to the width of two annules of the cuticle. The lateral fields are one-third as wide as the body. The granular renette cell, which is somewhat longer than the body is wide, and one fourth as wide as long, is located at a distance from the base of the neck equal to the width of the body, and empties by means of a slender duct, through the excretory pore located at the lips. It has a smaller companion cell in its rear. The nerve-ring surrounds the oesophagus somewhat squarely. The cells in its vicinity are distinct in character, and many of them have narrow connections directed forward. From the obscurely depressed somewhat conspicuous vulva, the small tubular vagina leads inward at right angles to the ventral surface one-third the distance across the body. The eggs are about as long as the body is wide, and usually about three-fourths as wide as long, and have been seen in the uterus one to three at a time. The spermatozoa seen in the females are one-eighth as wide as the body. The tapering ovaries reach about three- fourths the distance back to the vulva, and contain each about fifteen mostly dis- coid ova, arranged more or less single file. Habitat; remarks. Bay, Cape Royds. Five females in fair condition. 15. Chromadora polaris, n. sp. This species closely resembles Chromadora me- ridiana from the same region, but differs in having narrower dimensions, more FREE-LIVING NEMATODES 23 slender oesophagus, bulb and intestine, a / eo more strictly conoid tail, and a somewhat .'-- -'-> i. r .a thinner cuticule, the striations of which are even less modified on the lateral fields. There are about four hundred and fifty transverse striae. The cuticle is hardly perceptibly modified on the lateral fields in the anterior half of the body, but in the posterior half, especially opposite the copulatory muscles, there is a distinct modification, which at its widest part is nearly twice as wide as one of the corresponding striae. The modification be- comes less pronounced behind the anus, and disappears near the terminus. The renette cell occurs at a distance behind the neck equal to twice the diameter of the body. The stoutish, somewhat tapering, rather blunt, yellowish spicula are one and one-fourth times as long as the anal body diameter, and at their widest point one- sixth as wide as the body. They are almost imperceptibly cephalated by expan- sion and lie with their proximae a little ventral to the body axis. The frame has a median piece from near the middle onward. The two arcuate, slender, rather strong accessory pieces are three-fifths as long as the spicula and lie parallel to them. The seven chitinized supplementary organs, separated from each other by a distance equal to the diameter of one of the organs, occupy a space about equal to one and one-half times the body diameter, the posterior one occurring about opposite the proximal ends of the spicula. These organs are very much like those of Chromadora minor. The ejaculatory duct and vas deferens are one- fourth, the broad cylindroid testis one-half as wide as the body. Copulatory muscles extend forward somewhat beyond the supplementary organs. Habitat; remarks. Bay, Cape Royds. Two good specimens, both v male. SPILOPHORA, Bastian, 1865 The following are characters common to all the species of Spilophora here described. Cuticle with two lateral wings, beginning near the head and ending on the tail. Neck conoid. Tail tapering from somewhat in front of the anus. The lips are small and often indistinct, but when decipherable can usually be seen to be twelve in number, each with a single forward-pointing papilla. Throughout most of its length the oesophagus is more or less cylindroid, but ends posteriorly in a pyriform bulb two-thirds to four-fifths as wide as the base of the neck, and containing a fusiform valve (sometimes obscure) one-fourth to one-half as wide as itself. There is no distinct cardia. The intestine is separated from the oesophagus by a distinct broad constriction about one-third as wide as the corresponding part of the body. The more or less prominent chitinized rectum, about as long as the anal body diam- eter, leads inward and forward. The caudal setae are small and scattered. The nerve-ring is of medium size and surrounds the oesophagus rather squarely, and is accompanied by distinct nerve cells. The vulva is more or less elevated and con- spicuous and from it the vagina leads inward at right angles to the ventral surface about half way across the body. So far as known the eggs are ellipsoidal. The rather slender, blunt spicula are about one and one-fourth times as long as the anal body diameter. The arcuate accessory piece is parallel to, and half to three-fourths as long as, the spicula. The testis is relatively wide. 24 ANTARCTIC MARINE 16. Spilophora edentata, n. sp. Striae about 600, producing a crenate contour, interrupted by the two lateral wings which are so formed as to appear somewhat like the keel and ribs of a boat. Four sub-cephalic setae occur opposite the base Pi 7rT : - \-f ^-J^Lzk. 1 ^ 7 ---* 5 . 6 -- 8 !'- f the phar > rnx - There are gp .J^:j--.-Y i.~6~~3.2~r 3^3 3.~3 ~ 2 .e 1 least near the head. The cardiac 56 valve is simple in structure. The "*" 8 : > .SDD. relatively somewhat thick-walled 3-3 2 ' 6 intestine soon becomes two-thirds as wide as the body, and is about two cells in girth, these latter containing scattered, rather uniform, colorless granules. The posterior lip of the anus is more or less elevated. The cylindroid part of the tail is one-fifth as wide as the base, or somewhat less. The renette cell FREE-LIVING NEMATODES 25 has not been clearly seen, but the intestine is pushed to one side as if a small one were present, a little behind the neck. The nerve-cells extend past the base of the neck, especially on the ventral side. The eggs occur one at a time in either uterus. The rather broad, tapering ovaries, which extend two-thirds of the way back to the vulva, contain few ova, arranged single file. The testis is one-half to three-fifths as wide as the body. Habitat; remarks. Cape Royds; Bay, Cape Royds. Six females and three males, in a somewhat shrunken state. 18. Spilophora serrata, n. sp. Striae about 500, interrupted by the lateral wings, which occupy a space equal to one-fourth the body diameter. The second- ary elements of the cuticle j, ^ appear as dots on the head, pp ; ^0J!^\\ ?/u i-_ E _ : Ji'J_'_ 4 i' ^l*. 5 , and produce a punctate lffi '."'-|^v-' - 1>5 2>6 ; 2 ^1 3 - 4 2 - 5 appearance there. Four l'.-f^\ j K 1P . 8 .i7.i - H E9 86. rather irregular pairs of sub- sp 'jjlJE&Jfj l ~ E 2 V : ~ J V ~ 3 ~7 iT ' 9 "' cephalic setae, like the ceph- alic setae, but shorter, mated one in front of the other, occur at a distance from the lips equal to twice the width of the head. There are few cervical setae. The vestibule of the pharynx is longitudinally striated. This is one of the few species of Spilophora in which the amphids can be plainly seen. The rather thick- walled intestine soon becomes three-fourths as wide as the body, and is ten to twelve cells in girth, the cells containing numerous uniform, colorless granules nearly equal in diameter to the width of one of the annules of the cuticle. The posterior lip of the anus is elevated. The terminus of the tail is about one-sixth as wide as its base. The two broadly saccate caudal glands are arranged in close tandem opposite the anus and in the anterior fourth of the tail. Their ampullae are not distinct. The third caudal gland (?), just behind the anus, is a strongly staining cell, with a duct, or connection, that reaches to near the terminus. The non-granular renette cell, one body-width behind the neck, twice as long as the body is wide, has a small companion-cell in its rear. The excretory pore is probab- ly near the lips. Opposite the renette cell there are two, and probably three, ellipsoidal cells in each lateral field, each cell being one-third as long as the body is wide, and one-third as wide as long. These cells constitute two pairs, or three. The eggs are about one and one-half times as long as the body is wide, and two thirds as wide as long, and occur in the uteri one at a time. Each of the medium sized, tapering ovaries reaches half way back to the vulva, and contains about fifteen ova arranged single file. The strong, rather uniform, colorless spicula are cephalated by a constriction and are obliquely truncated at the distal end, where there are two or three exceed- ingly minute teeth. The subslender, rather strong and simple accessory pieces recede a little from the spicula. Of the slightly elevated, somewhat protrudable supplementary organs, whose width is about equal to that of two annules, the hindermost is near the anus. They are farther apart anteriorly, the distance between the first and second equaling one-third of the body width, that between the second and third, one and one-half times the body width. The ejaculatory duct is one-third as wide as the body the vas deferens and testis one-half. At least one pair of glands of the kind seen in the males of Euchromadora occurs nearly twice as far in front of the anus as the terminus is behind it; each gland-cell is 26 ANTARCTIC MARINE / fusiform, one-half as long as the body is wide, and one-half as wide as long. Both of the males examined had a ventral swelling near the center of the tail, as long as the corresponding body diameter. Habitat ; remarks. Bay, Cape Royds. The two females and two males studied were in good condition. EUCHROMADORA, De Man, 1886 The following are characters common to all the species of Euchromadora here described. The neck is more or less cylindroid in the posterior part, but usually slightly conoid anteriorly. The tail tapers from in front of the anus, and has no terminal swelling. Cervical setae none or small and scattered, except in E. septentrionalis, somatic setae none or very inconspicuous. Caudal setae none or inconspicuous, except in E. denticulata. Each of the six lips is double, so that there appear to be twelve more or less alike. These are usually distinct when the mouth is open, but so folded together when the mouth is closed as to become less distinct, and to impart to the then narrow vestibule a longitudinally striated appearance. Labial papillae twelve, in a single circlet, forming the apices of the lobes of the lips. The pharyngeal region of the oesophagus is swollen, so as to form a faint pharyngeal "bulb," rather obscurely pyriform or elongated in form. The oesophagus is cylin- droid in the anterior half, and conoid or perhaps clavate in the posterior part, but is without a true cardiac bulb except in E. septentrionalis. Oesophageal lining distinct, often increased posteriorly. There is no distinct cardia. The rather thin walled intestine becomes almost at once three-fifths to three- fourths as wide as the body and is from six to nine cells in girth. It is separated from the oesophagus by a distinct collum one-fifth to one-third as wide as the corresponding part of the body. The chitinous rectum, as long as the anal body diameter, leads inward and forward from the more or less elevated anus. The caudal glands are found in the anterior fourth of the tail (and in E. meridiana also a short distance in front of anus), and empty through ducts devoid of ampullae, except in the case of E. denticulata. The lateral fields are about one-third as wide as the body. The elongated, granular renette cell, one to two body-widths behind the neck, has one or two smaller companion cells in its rear. The medium sized nerve-ring surrounds the oesophagus rather squarely. From the somewhat ele- vated but rather inconspicuous vulva the vagina leads inward at right angles to the ventral surface about halfway across the body. The reflexed, tapering ovaries reach half to two-thirds the way back to the vulva, and contain a dozen or more de- veloping ova, arranged more or less irregularly, especially toward the blind end. The more or less slender spicula are sub-acute, and accompanied by arcuate parallel accessory pieces half as long as themselves. The single testis is cylindroid and about half as wide as the body. 19. Euchromadora septentrionalis, n. sp. The 600 striae, very difficult to see except at the extremities, are resolvable into minute elongated elements, which are interrupted by very narrow and inconspicuous lateral 3.2 2.3 ' wings, beginning near the head 55 and ceasing near the end of the 1. 6 10.4_,_16.6 -M 88. , y 2 y. y y s - 3 y .. tail. Two sub-cephalic setae, nearly as long as the cephalic FREE-LIVING NEMATODES 27 setae, occur one in front of the other on each sub-median line, at a distance from the head end equal to one and one-fourth times the head width. The cervical setae, more numerous on the anterior part of the neck/ are sometimes longer than the cephalic setae. The lips, otherwise typical, have successive rings of elements surrounding the interior of the vestibule. The oesophagus is one-third as wide as the neck, but swells posteriorly into a true cardiac bulb, containing a fusiform valve one-third as wide as itself. The intestinal granules are scarce and colorless. The elongated caudal glands are arranged in a close tandem, and have distinct ducts. The renette cell, three times as long as the body is wide, empties through a very inconspicuous pore at the base of the lips. Strongly staining, elongated, distinctly granular bodies are found in the lateral fields behind the neck. They are one-half as long as the body is wide, and two-thirds as wide as long, and they occur as rightsand lefts, i. e. are paired. The first pair is one body-width behind the neck, and the successive pairs, continuing to the anus, are separated from each other by a distance three times as great as the radius of the body. The tail of the male is a little stouter than that of his mate. The uniform, slender, frail spicula are as long as the anal body diameter, and one-twelfth as wide as long. There are two strong grooved accessory pieces, twice as wide as the spicula, bearing excessively minute teeth at their blunt distal ends. There are at least five unicellular clavate glands on the dorsal side, extending in front of the anus for a distance equal to the length of the tail. First, anteriorly there is a pair, then a second pair, then apparently a single one, all with slender ducts They were not very well seen, and this enumeration may not be exact. Habitat; remarks. Cape Royds; Bay, Cape Royds. Numerous specimens, somewhat shrunken. 20. Euchromadora antarctica, n. sp. The cuticle is traversed by about 550 transverse striae, resolvable into dots near the head, and into basketwork-like markings on the neck and else- where. These striae are of such a size as to give rise to an obscurely crenate contour line. There is a simple, very obscure cardiac valve, one-third as wide as the base of the oesophagus. The cells of the intestine contain numerous rather small, colorless, uniform granules. The ellipsoidal caudal glands are ar- ranged in a loose tandem, and empty through very narrow ducts. The renette cell is about as long as the body is wide, and one-third as wide as long, and presses the intestine somewhat to one side. The nerve-cells around the oesophagus are of a distinct character, but are scattered so as to exhibit no very systematic arrangement. The prolate to ellipsoidal eggs are considerably longer than the body is wide, and three-fourths as wide as long. They have been seen in the uterus one at a time. The tapering ovaries contain upwards of a dozen ova. The slender, uniform spicula have a more or less frail framework, and are about twice as long as the anal body-diameter. They are not cephalated, but the proxi- mal parts are somewhat wider. This wider part lies a little to the ventral side of the body-axis, that is, it appears to do so when the animal is viewed in profile. The single, slender accessory piece has a framework that is more or less frail, and has its proximal end opposite the body-axis. The supplementary organs are 28 ANTARCTIC MARINE spread along a distance about equal to five or six body-diameters, the distance between the adjacent organs being about equal to the radius of the body. These organs. are of such a nature that when the body is stretched out they hardly dis- turb the ventral contour, but when the tail end is incurved, as is often the case, they become slightly raised, so that the altitude is about equal to one-half the width of one of the annules of the cuticle. In this contracted condition of the ventral surface of the body the distance between the organs is about equal to their own diameter. The ejaculatory duct is one-fourth, the vas deferens three- fourths, and the testis two-fifths as wide as the corresponding portions of the body. The testis is cylindroid. Rather distinct, oblique copulatory muscles are found coextensive with the supplementary organs. Habitat; remarks. Cape Royds; Bay, Cape Royds. Numerous specimens, somewhat shrunken. 21. Euchromadora denticulata, n. sp. Striae about 400, resolvable into bas- ketwork-like markings of a rather obscure character on the anterior part of the neck. The lips are sub- 2.4 14.' 26. 53 Y 83. distinct. At the nerve- ~I.~2~~ir4~~I.~7~~3.~V ring the oesophagus has a diameter equal to two- fifths the corresponding diameter of the neck, but swells posteriorly to three-fourths the corresponding diameter. In the posterior swelling the lining is somewhat expanded. The dimly seen pyloric collum is one-third as wide as the body. Intestinal granules are scarce. The ellipsoidal caudal glands occur in a close tandem opposite the anus and in the anterior fourth of the rather massive tail. The caudal setae, six ventro-submedian, and six dorso-submedian, are slender, stiff, somewhat cylindroid, sub-acute, and one-sixth as long as the anal body-width. The renette-cell, two-thirds as long as the body is wide and one-third as wide as long, empties through a pore opposite the nerve-ring. In both the specimens examined there appears a slender seta-like appendage (?) at the mouth of the excretory pore. The female reproductive organs are double and symmetrical, and probably reflexed. Habitat; remarks. Cape Royds. Two females, in fair condition. 22. Euchromadora meridiana, n. sp. The cuticle is much like that of Euchro- madora vulgaris, (Bast.) de Man. 400 striae, retrorse posteriorly and the reverse anteriorly, make the con- 33 tour obscurely crenate. PP " \l^V~ JL_ 6 J_ 4 ^- 1 _i: l The oesophagus, cylin- droid anteriorly, conoid < . - < posteriorly, has several ...... 8 . 4 breaks in its muscula- ture, the most prominent being at the beginning of the final fifth of the neck. The numerous intestinal granules are small, uniform, and indistinct. The rather ellipsoidal caudal glands are arranged in an open tandem. Immediately behind the anus the tail has a diameter equal to three-fourths the anal body-diameter; thence onward it tapers but very slightly to the middle, where it begins to taper more rapidly to the terminus which is one-third as wide as the anal body-diameter. The lateral fields are somewhat distinctly cellular. The renette-cell, which pushes FREE-LIVING NEMATODES 29 the intestine to one side, is twice as long as the body is wide, one-fourth to one- fifth as wide as long. Just behind the nerve-ring there is a large ampulla as long as the body is wide, and one-third as wide as long. In all the specimens examined there appears a slender seta-like appendage at the mouth of the excre- tory pore somewhat longer than the cuticle is thick. The ovaries are broad. The male tail is like that of the female, but more uniformly tapering, with less of a diminution just behind the anus. The strongly arcuate, sub-slender, rather strong and tapering spicula, somewhat cephalated at the tapered distal ends, are one and two-thirds times as long as the anal body-diameter, and lie with their proximae slightly ventral to the body-axis. There are two, more or less separate accessory pieces, each in two parts, one behind the spicula; the other in front or alongside, the front part being like a reduced spiculum. The ejaculatory duct is one-fifth, the vas deferens one-half as wide as the body. Habitat; remarks. Cape Royds; Bay. About a dozen somewhat shrunken specimens, the two sexes occurring in about equal numbers. LAXUS, Cobb, 1894 23. Laxus septentrionalis, n. sp. There are upwards of 1000 plain, transverse striae so small as to be difficult of resolution. The three subdistinct, more or less bluntly conoid lips are united by a mem- brane, and form a circlet around the mouth, very difficult to see, except when the mouth is open. Only when the mouth is open can the connecting membrane be seen. It is prob- able that the pharynx contains an obscure dorsal tooth. The structure which gives rise to this supposition is of fair size, and thinly covered w y ith chitin. The cylindroid to conoid neck contains a cylindroid oesophagus, which, measured near the nerve-ring, is one-half as wide as the corresponding portion of the neck. Though the amphids appear circular, they are in reality spiroidal. The pharynx is situated in the midst of an almost imperceptible elongated pharyngeal swell- ing, two-thirds as wide as the head. The thick walled intestine, six cells in girth, soon becomes five-sixths as wide as the body. It has a distinct lumen, and is separated from the oesophagus by a collum hardly one-third as wide as the base of the neck. For a distance about equal to the length of the body-diameter the cells of the intestine are comparatively free from granules. Thereafter they are uniformly packed with yellowish granules having a width a little greater than that of one of the striae of the cuticle. From the continuous anus the prominent, chitinized rectum extends inward and forward a distance three-fourths as great as the length of the anal body-diameter. The tail tapers froni the anus to a terminus one-third as wide as its base. Ap- parently the ellipsoidal caudal glands are packed together somewhat behind the middle of the tail. Their ampullae, near the terminus, are more or less distinct. The lateral fields, which are one-third as wide as the body, are margined by re- fractive lines, at least in balsam specimens. The renette has not been clearly seen, but is supposed to be located at a distance behind the neck equal to the 30 ANTARCTIC MARINE radius of the body, and to be about one-half as long as the body is wide, and one- half as wide as long. It empties by means of a short duct, and a rather struc- tureless ampulla half as wide as the oesophagus, through the excretory pore near the nerve-ring. The vulva is more or less continuous, and rather inconspicuous. The elongated eggs are one and one-half times as long as the body is wide, and one-third as wide as the body. They have conspicuous nuclei. Of the narrow ovaries the posterior one is only one-third to one-half as long as the anterior, which contains twenty developing ova, arranged single file, while the posterior one contains only about fifteen. The slender, uniform spicula have a more or less frail framework. The single accessory piece, also more or less frail, presents,a stoutish, uniform, blunt apoph- ysis one-half as long as the anal body-diameter, arranged at right angles to the part which is applied to the spicula. This latter is one-third as long as the spic- ula. The vas deferens is one-third, the tapering testes about one-half as wide as the body. These latter, however, finally become very narrow. The blind end of the posterior testis lies in front of the anus a distance about equal to six times the length of the tail. Habitat; remarks. Bay, Cape Royds; Bay. Four females and two males, slightly shrunken. AXOXOLAIMUS, de Man, 1889 24. Axonolaimus polaris, n. sp. The striae of the thin cuticle are very difficult to resolve and are best seen on and near the tail. One is left in doubt as to whether 4 9 7 3 Y 94.7 the COnt Ur is P lain > or Vei T mi ' ' '", i-7r.n. nutely crenate. Apparently there are six subcephalic setae, each half as long as the diameter of the head measured at the labial CP \ ' \ constriction. Though there are no somatic setae there are a few scattered setae on the neck, generally somewhat shorter than the subcephalic setae. The conoid neck contains a conoid oesophagus, whose diameter near the nerve-ring is two-fifths as great as that of the corre- sponding part of the neck, and which finally becomes two-thirds as wide as the base of the neck. There is no distinct cardia. The thick walled intestine is two to three cells in girth, and becomes at once three-fourths as wide as the body, being separated from the oesophagus by a collum three-fifths as wide as the base of the neck. On account of the food contained in it the lumen of the intestine is distinct. The intestinal cells contain very fine, scattered, colorless granules in the middle of which the nucleus appears as a distinct feature in stained specimens. From the raised anus the chitinized rectum extends inward and forward a distance equal to the anal body-diameter. The tail tapers from the anus, bears very minute hairs near the end, and contains broadly saccate caudal glands packed in its anterior third. The nerve-ring surrounds the oesoph- agus squarely, is of medium size, and is accompanied by obscure nerve-cells, which are not very distinctly grouped. Habitat; remarks. Bay, Cape Royds. Single young specimen, in fair con- dition. In the sketch the lips are shown partly everted. FREE-LIVING NEMATODES 31 THORACOSTOMA, Marion, 1870 25. Thoracostoma polare, n. sp. The thick yellow cuticle is traversed by mi- nute, transverse striae difficult of resolution, and in its deeper layers, at least near the head, by fine ^_ J V ^ 38 oblique striae crossing each lfc -1^ V\ : - - 8 - 14< t<5 ' "' ? other at an angle of about pc .--/t--r*f' ^ \ ' 4 1- " 3 1-5 ' 8 forty-five degrees. Subce- \*-'ffij$M\ .2 4.9 12. _ M - 69 99.4 phahc setae, like the ce- \^r^\\\j/^ \ .4 i'g i';' 3 ' i'T '^ i9.a phalic in form and size, oc- cur in groups of three or four together, near the border of the "cuirasse," and a little farther back. Similar cervical setae occur on the anterior part of the neck singly and separated by a distance one-fourth to one-third as great as the diame- ter of the neck measured at the middle. The remaining cervical setae as well as the somatic setae are reduced to papillae. All these setae are arranged in more or less irregular lateral and submedian lines. The head is furnished with a chiti- nous, faintly yellowish "cuirasse," extending back to opposite the base of the pharynx, and divided longitudinally into six lobes by as many sutures. Each of these lobes is perforated near the posterior margin by two oblique, irregular locules, each a little more than half as long as the amphids are wide. The three amalgamated lips are nearly obsolete. Six forward pointing, inconspicuous, in- nervated papillae form a single circlet on the front of the head. The simple, rather narrow, more or less irregularly pyramidal, well chitinized pharynx is as long as the head is wide, and is somewhat narrowed posteriorly, where the two ventrally submedian oesophageal glands empty into it. The third oesophageal gland, ventral in position, empties into the lumen of the oesophagus a little more than halfway back to the eye-spots. When shut the pharynx rather closely resembles the lumen of the oesophagus, which possesses a well developed chiti- nous lining. The only armature of the pharynx is the dorsal, labial, two-lobed cordiform piece of chitin just at the mouth opening, arranged much as described by Dr. de Man for Thoracostoma antarcticum, v. Linst. Two faint refractive lines close together lead backward from the posterior part of each amphid. The two rather widely separated eye-spots are located at a distance from the anterior extremity equal to four times the width of the head, and are one-sixth as wide as the corresponding part of the neck, and about as long as wide. These are somewhat heart shaped, and are composed of compactly arranged brownish granules. There are obscure indications of a refractive body, or "lens," in the hollowed out front part of each eye-spot. The conoid oesophagus is about half as wide as the neck, and presents a faint, elongated pharyngeal swelling. The cylindroid cardia is one-fifth to one-fourth as wide as the base of the neck. The thick-walled intestine, separated from the oesophagus by a collum one-third as wide as the base of the neck, becomes at once three-fifths as wide as the body, and is about six cells in girth. The intestinal cells contain numerous uniform, colorless granules. The posterior lip of the anus is slightly elevated. The hemispherical-conoid to convex-conoid tail tapers from the anus and ends in a very broad, bluntly rounded terminus. The spinneret is a very slightly depressed pore with a suggestion of yellowish color, arranged a little unsymmetri- cally, so that it empties somewhat toward the ventral side, and not axially. It 32 AXTARCTIC MARINE is unarmed, though a little in front of it there are a very few papilla-like setae. The three more or less elongated saccate caudal glands extend in a loose tandem in front of the anus a distance five times as great as the corresponding body- diameter. Their distinct and somewhat tortuous ducts widen to three separate ampullae so as to fill the middle of the tail. The vulva is slightly depressed and is rather inconspicuous. The vagina extends inward at right angles to the ven- tral surface about halfway across the body. Both before and behind the vulva there are well developed unicellular glands. Each of the two straight uteri is about seven times as long as the body is wide, and contains a row of five or six eggs in the specimens examined. The rather thick-shelled eggs are three-fourths as long as the body is wide, and nearly as wide as long. Owing to their pressure on each other the eggs take on a more or less rectangular contour. The broad ova- ries reach two-thirds the way back to the vulva, and contain scores of discoid ova, arranged more or less in single file. The anus of the male is broadly elevated. The tail of the male has a compli- cated sexual armature. Near the anus on the anterior fourth of the tail there are six stout, stiff, conoid, somewhat blunt, ventrally submedian setae on each side, the longest of which, those nearest the anus, are nearly as long as the cuti- cle is thick, and the smallest of which, the hindermost, are very small. The pre- anal setae are arranged in ventrally submedian rows, of which the individual setae are much nearer together posteriorly than anteriorly. Between the anus and the single ventral median supplementary organ there are ten of these setae; between the latter and the posterior member of the ventrally submedian rows of supplementary organs there are two of these setae; between the ultimate and the penultimate members of the submedian series there are also two. Thence forward between any two members of the submedian series there is but a single seta. In all, therefore, there are about seventeen of these setae on each submedi- an line in front of the anus. In addition there are two very inconspicuous, papil- loid, tapering, acute, lateral setae near the terminus. The lateral fields, one-third to two-fifths as wide as the body, are composed of several rows of cells among which are placed glandular, saccate cells, of two or three times as great diameter, connected with the exterior by means of pores in the cuticle. The relative num- ber and position of these glandular cells may be judged to a certain extent from the fact that in the female near the vulva three of these large saccate cells are separated from each other by spaces about equal to their own diameter. These cells are entirely similar to those described by Jaegerskiold, de Man, and other authors, who have made observations on species of Thoracostoma. The distinct cells connected with the more or less broad and oblique nerve-ring are arranged into rather distinct groups and are a prominent feature of the middle half of the neck. The stout, blunt, yellowish spicula, cephalated by a very slight constriction, are arcuate in the distal half, and are one and three-fourths times as long as the anal body-diameter. At the widest part, a little in front of the middle, they are about one-fourth as wide as the corresponding part of the body. From the widest part they taper gradually to the distal ends, but taper more suddenly toward the proximal ends, which lie opposite the body-axis and have a width when viewed in profile about twice as great as the thickness of the adjacent cuti- cle on the dorsal side of the body. The difference between the anterior and pos- FREE-LIVING NEMATODES 33 terior parts of the spicula is greater than in Thoracostoma setosum, Linst. The strong, chitinous framework is strengthened by a middle piece in the distal three- fifths. The two separate, strong, rather stout accessory pieces are bent a very little, and are half as long as the spicula. They are of somewhat irregular width, but appear when seen in profile about twice as wide as the dorsal cuticle is thick. They lie parallel to the spicula, but their cephalated proximal ends, a little wider than those of the spicula, are bent away a little and lie somewhat to the dorsal side of the body-axis. The elevated, mammiform supplementary organs, about one-sixth as wide as the body and half as high as wide, are arranged in ventrally submedian rows one and two-thirds times as long as the body is wide, the posterior members being located a distance in front of the anus equal to one and two-thirds times the length of the spicula. They are a little farther apart posteriorly than anteriorly, the longest space being about equal to the length of the radius of the body as seen in profile at the corresponding part. In addition to these two rows of five organs each there is a single ventral organ a little in front of the middle of the spiciila, similar in size and form to the others, but manifestly of a different structure. Sometimes there is an appearance as if a rudimentary sixth ventrally submedian organ is present in front of the fifth. Oblique copulatory muscles are arranged close together coextensive with the supplementary organs. The ejaculatory duct is about one-fifth as wide as the corresponding part of the body. Habitat; remarks. Bay, Cape Royds; Cape Royds. Three females and two males, in good condition. February, 1914. NORTH AMERICAN FREE-LIVING FRESH-WATER NEMATODES CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY II BY N. A. COBB (With eighty illustrations) INTRODUCTION. The little creatures described in these pages belong to a very important but as yet comparatively little known class of animal organisms, the nematodes. Something more than a mere reconnaissance leads to the con- clusion that over nine-tenths of the nematode species still remain unknown, a greater disproportion between the known and the un- known than exists in almost any other class of organisms. Nematodes are distributed far and wide in inconceivable num- bers, and without doubt constitute a group in the animal kingdom comparable with insects both in number of species and economic importance. They vary in length from one two-hundredth of an inch to several feet, though the great majority are less than half an inch long. They differ from most other slender, wormlike forms in their lack of locomotive appendages, the outer surface, except for the presence of setae, is usually quite smooth. Being more or less cylindrical in form, they are often called "round-worms." They live free in the soil, in fresh and salt water, and are found parasitic in a great variety of animals and plants. NEMATODES AS CAUSES OF DISEASE The parasitic species often cause fatal diseases of plants and of animals, including mankind. The dreaded hookworm is a nema- tode. So is that scourge of the tropics, the guinea worm. Trichina,* "Trichinella spiralis. Reprinted from Trans. American Microscopical Society. Vol. XXXIII, April, 1914. 36 NORTH AMERICAN costing civilized nations hundreds of thousands of dollars yearly for the inspection of pork, is a nematode. If trichina,-infested or measly pork be eaten by human beings, the result is a serious, often- times fatal, sickness, called trichinosis, epidemics of which have claimed victims by the hundred. Nematodes have recently been suspected, with good show of reason, of being carriers of cancer. So the list of serious human nematode diseases might be increased until practically half a hundred had been enumerated. No less serious are the nematode diseases of plants and of the lower animals. The common gall-worm has been found infest- ing the roots of several hundred different species of plants, among them most of our cultivated crops, and causes a'n annual loss amounting to millions of dollars. There is another nematode that has at times completely checked the growing of sugar beets in cer- tain regions. The list of serious plant diseases of this character could easily be increased to scores. The same is true of animals. Every domestic, doubtless every wild, species has a number of specific nematode parasites sapping its vitality. WONDERFUL VARIETY OF HABITAT. Not the least interesting thing about nematodes is the astound- ing variety of their habitats. They occur in arid deserts and at the bottoms of lakes and rivers, in the waters of hot springs and in polar seas where the temperature is constantly below the freezing point of pure water. They were thawed out alive from Antarctic ice in the far south by members of the Shackelton expedition. They occur at enormous depths in Alpine lakes and in the ocean. As parasites of fishes they traverse the seas ; as parasites of birds they float across continents and over high mountain ranges. Their eggs and larvae, invariably of microscopic size, are carried from place to place by an exceedingly great variety of agencies. Almost any vis- ible thing that moves is capable of transporting nematode eggs or larvae. Sometimes the eggs and larvae are so resistant to dryness that if converted to dust they revive when moistened. This revival of mummified nematodes may take place after as long a period as a quarter of a century. Nematodes are found in queer places. The wildest imagina- tion could hardly outpicture the facts. One species is found prac- FREE-LIVING FRESH-WATER NEMATODES 37 tically only in the vermiform appendix of man; another has its adult form only, in the seeds of wheat. A third form occurs in the felt mats on which the Germans are accustomed to set their mugs of beer, and has been found in no other habitat. On the feet of birds and insects the eggs, larvae, and adults of certain nema- todes are carried to the tops of the tallest trees. The sour sap is- suing from the wounds of a tree, often many feet above the ground, not infrequently contains nematodes that are specific to the wounds of that particular kind of tree. The tap water of even well-con- ducted cities often contains nematodes. Nematodes are inconceivably abundant. A thimbleful of mud from the bottom of the ocean may contain hundreds of specimens. The number of nematodes in the top six inches of an acre of ordi- nary arable soil amounts to thousands of millions. Statistical cal- culations relative to the number of nematodes in a single acre of soil near San Antonio, Texas, U. S. A., disclosed that if they could start in a procession for Washington, D. C., two thousand miles away, each close on the tail of the one in front, the head of the procession would reach Washington before the rear had left San Antonio. As nematodes are usually very prolific, a single female sometimes producing thousands of eggs, the number of eggs vastly exceeds that of the adults". We must therefore conceive of nematodes and their eggs as being carried by the wind, and by flying birds and running animals ; as floating from place to place in nearly all the waters of the earth ; and as shipped from point to point throughout the civilized world in vehicles of traffic. There are beneficial nematodes, though knowledge of this phase of the subject is in its earliest infancy. Some nematodes feed ex- clusively on their injurious brethren. Others devour baneful micro- organisms. Their adaptations and relationships appear to be sim- ilar to those of insects. NORTH AMERICAN FRESH-WATER SPECIES. The nematodes here described are the main portion of those found during a rather casual search for aquatic species that would serve as the basis of a special chapter in a zoological textbook de- voted to fresh water organisms. The object of the textbook was 287184 38 NORTH AMERICAN to characterize each known genus by describing and illustrating a typical species. When the work on the nematode chapter was begun there was hardly a single adequately described North American species, so that the initial task was one of pure discovery. This was followed by the work of research and definition, and this finally by that of selection and presentation of typical species in a manner suitable to a college textbook. The famous Philadelphian, Dr. Joseph Leidy, appears to be the only naturalist who had previously attempted to describe any of our fresh water nematodes, and even he did but little. I have at- tempted to rehabilitate his Anguilhda longa, which, as Bastian sur- mised, belongs to the more modern genus Trilobus. I have had to assume that the variety Leidy had before him was that most com- mon in the ditches, brooks and rivers of the Chesapeake region, and have given to this form the name Trilobus longus (Leidy) Bastian. All the other species proved to be new, some of them repre- sentatives of new genera. Most of the new genera have already been described in my contribution to the Proceedings of the Wash- ington Academy of Sciences, October, 1913. An aquatic species as here defined is any species inhabiting either fresh water, or non-brackish swampy soil below the water table ; hence a species that will not drown in fresh water ; a species fitted to utilize oxygen dissolved in fresh water. Including those of the present article, the fresh water North American species so far described are as follows : Achromadora minima Cyatholaimus truncatus Actinolaimus radiatus Diplogaster fictor, Bastian Alaimus simplex Dolichodorus heterocephalus Anonchus monhystera Dorylaimus fecundus Aphanolaimus minor Ethmolaimus americanus Aphanolaimus spirurus Iota octangulare Bastiana exilis Ironus americanus Cephalobus setosus Mesomermis virginiana Cephalobus subelongatus Microlaimus fluviatilis Chronogaster gracilis Monhystera sentiens Cryptonchus nudus Mononchus similis FREE-LIVING FRESH-WATER NEMATODES 39 Oncholaimus punctatus Spilophora canadensis Plectus tubifer Teratocephalus cornutus Prismatolaimus stenurus Trilobus longus (Leidy), Ba'stian Rhabditis punctatus Tripyla lata Rhabdolaimus minor Tylcnchus symmetricus There has been little time or opportunity to search specially for these fresh water forms, and the fact that it has been possible in so short a time to assemble so many genera and species is proof of the enormous abundance and multifarious nature of these organ- isms. No doubt there is a horde of species awaiting discovery in North American waters. THE NEMATODE FORMULA. The following diagram illustrates the nature of the formula used in the tabulation of the various necessary measurements : =?#; Fig. 1. Diagram of the descriptive decimal formula used for nematodes; 6, 7, 8, 10, 6 are the transverse measurements, while 7, 14, 28, 50, 88 are the corresponding longi- tudinal measurements. The formula in this case is: 7. 14. 28. SO. 88. 6. 7. 8. 10. 6. The unit of measurement is the hundreth part of the length of the body, whatever that may be. The measurements become, therefore, percentages of the length. The absolute length is given in millimeters as a final non-paired term. This decimal method of presenting the measurements is the most compact and convenient method, and is being used more and more year by year. The measurements are taken with the animal viewed in profile ; the first are taken at the base of the pharynx, the second at the nerve-ring, the third at the cardiac constriction or end of the neck, the fourth at the vulva in females and at the middle (M) in males, the fifth at the anus. The formulae represent the average of sev- eral specimens whenever possible. There are several methods of securing the measurements, one of the most convenient being the preparation of a camera lucida "skeleton" to scale, consisting of a line following the body axis 4O NORTH AMERICAN from one end to the other, and diametral lines at the base of the pharynx, the nerve-ring, the end of the neck, at the vulva in fe- males and at the middle in males, and finally at the anus. This skeleton is then measured with a metric scale and map measure, and the percentages divided out with the aid of a slide rule. IOTA, Cobb, 1913. Fig. 1, Plate II. 57 14. 21. 25. -85 Q2. 1. Iota octangulare, n.sp. .4 mm. II. 12. 12. 9. 6. Along the longitudinal fields the striae are so modified as to give the worm somewhat the appearance of being covered by eight rows of relatively large scales arranged in pairs. Six small, simple, flattish lips surround the vestibule. The lips are supplied with six small, innervated papillae. These lie in the midst of a plate-shaped disk, the first annule. There are no recog- nized traces of amphids, but the recessive nature of the second annule is suggestive, and it is possible that this peculiarity of the second annule is in some way connected with the amphids. There are no eye-spots. The narrow vestibule leads to the equally narrow pharynx, which consists essentially of a muscular tube closely surrounding the spear. This latter is of relatively very large size, and strictly Tylenchoid in structure. Its length is about equivalent to the first twelve annules of the cuticle. It is divisible into two parts : a long cylindrical hollow shaft tapering to a point near its apex, and having a length about equivalent to the first nine annules ; behind this shaft a basal portion or "hilt," which in its distal part has a structure like that of the shaft, but with a slightly greater diameter. This hilt terminates in a threefold, flattish bulb about one-fourth as wide as the corresponding por- tion of the neck. The lumen of the spear is continuous with that of the oesophagus. This latter consists mainly of a narrow, chitinous tube, which is usually somewhat coiled when the spear is at rest. That portion of the oesophagus containing the hilt of the spear and the coiled oesophageal tube just mentioned constitutes a somewhat obscure elongated "bulb." This bulb, however, is not the morphological equivalent of the bulb usually seen in the oesophagus of Tylenchus and Aphelenchus, as it has no radial muscles, and contains no valvular apparatus. The remaining short portion of the oesopha- gus is tubular and narrow, though it swells slightly at the terminus, where it is about one-eighth to one-ninth as wide as the base of the neck. The ex- cretory pore empties through the exterior margin of the nineteenth annule, or thereabouts. It may be distinctly seen when the worm is viewed from the ventral side, and less distinctly seen in profile. Habitat: Dismal Swamp, Va. Flemming solution to glycerine. FREE-LIVING FRESH-WATER NEMATODES 41 RHABDOLAIMUS, de Man, 1880. Fig. 2, Plate II. 28 2. Rhabdolaimus minor, n.sp. 4 ' 6 * 5 ' ^ <5I> 77 ' 5 2 8 mm 2.4 37 3-8 4- 2. The thin layers of the transparent, naked, colorless cuticle appear to be destitute of any but very fine transverse striations, most clearly visible near the head. The conoid neck ends in a rounded head which is not set off in any way. There are no cephalic setae. Careful focussing appears to indicate on the outer margin of the head the presence of almost invisible papilla-like or- gans which may perhaps be representatives of cephalic setae. There are no lips. The amphids are located at a distance from the anterior extremity about three times as great as the width of the lip-region, and a little more than twice as great as the width of the head near where they occur. Seen in dorso-ventral view they have the appearance of obscure openings from which there leads inward and backward slight refractive elements which soon become indefinite. Immediately behind the mouth opening there is at least one obscure refractive element of small size, apparently very much as figured by Dr. de Man in his description of the type species. The tubular pharynx is long and slender, extending backward for a considerable distance behind the amphids. Its total length is probably a little less than one-third the distance to the nerve-ring, though the limits are not definite in the speci- mens so far examined. The oesophagus is at first about three-fourths as wide as the head and continues to have this diameter, or a slightly greater diameter, until near the end, where it expands to form the pyriform cardiac bulb which contains an obscure valvular apparatus. This bulb is three- fourths as wide as the base of the neck. The lining of the oesophagus may be faintly seen throughout its length. The rather thin-walled intestine which is separated from the oesophagus by a slight constriction becomes at once three-fourths as wide as the body. It appears to be composed of cells of such size that probably only four to six are required to build a circumfer- ence. From the nearly continuous anus, the rectum, which is somewhat longer than the anal body diameter, extends inward and forward. The tail begins to taper from a little in front of the anus and tapers regularly to the terminus which is armed with a striking, elongated, unarmed, slightly tapering, acute spinneret. Where the tail joins the spinneret the diameter is about one-fifth as great as at the anus. There is a sudden and very slight diminution of diameter of the terminus where it joins the spinneret. From the inconspicuous vulva, the vagina leads inward and forward. The sym- metrically reflexed ovaries reach about half way back to the vulva. The thin-shelled, smooth eggs are relatively large and elongated and have been seen in the uterus one at a time. They are about four to five times as long as the body is wide and about one-fifth as wide as long. They appear to be deposited before segmentation begins. Habitat: Mud, Beach pool, Pine Point, Douglas Lake, Michigan. Sublimate to balsam. 42 NORTH AMERICAN DIPLOGASTER, Max Schultz, 1857. Fig. 3, Plate II. 35 1.3 10.7 13.8 '51' 88.1 3. Diplogaster fictor, Bastian 1.5 mm. 1.3 1.4 1.4 1.7 1.4 The thin layers of the transparent, colorless, practically naked cuticle are traversed by exceedingly fine transverse striae, resolvable with high powers under favorable conditions, which become considerably coarser to- ward the head, where they are resolvable into rows of refractive dots ar- ranged in longitudinal, as well as transverse lines. A short distance behind the head the longitudinal rows arrange themselves in pairs. These pairs indicate the locus of about twenty-four cuticular ribs or wings, which extend from the middle of the neck to near the anus. On the tail these ribs again resolve themselves into double rows of dots, and gradually disappear as the tail grows narrower. Very little is to be seen of them behind the middle of the tail. The cylindroid neck ends in a somewhat rounded head, which bears near its outer margin a circlet of six somewhat forward-pointing, tapering cephalic setae, each about one-third as long as the head is wide. There is one of these setae on each submedian line and one on each lateral line. Just in front of the base of each lateral seta a minute obscure pore or papilla was observed, which did not appear to exist in connection with the other setae. The amphids, though only faintly visible, are of relatively large size. Their form is partly indicated by a lateral area on which the punctations of the cuticle are absent. This is a somewhat elliptical area placed transversely on the side of the head, with its long axis at right angles to the lateral line. Its length is equal to half that of the correspond- ing diameter of the head. Its anterior contour is more definite than the posterior, although it is only by the most caerful focusing that the defintie line of contour can be distinguished. Through the middle of the area, how- ever, there is quite a distinct arcuate line, with its convex side toward the lips. When seen dorso-ventrally the amphids have the appearance of distinct oblique openings, leading inward and backward. When the mouth is opened and the lips recurved the amphids are moved forward somewhat and the transverse line mentioned becomes more strongly curved and forms a semi-circumference. The circular mouth opening is very finely striated on the inner surface of the lip region. These striae begin on the inner face of the lips near where the cuticular wall of the pharynx first appears. They extend backward nearly to the base of the pharynx and end in- definitely. In front of this finely longitudinally striated area the transverse marginal portion of the lips is more coarsely divided into fourteen parts. The lips are capable of being opened, so that the oral aperture is two-thirds as wide as the head. Under such circumstances it is seen that the lip region is flower-like in form with fourteen recurved seg- ments, the distal tapering portion of each of which is plain and FREE-LIVING FRESH-WATER NEMATODES 43 transparent, while the basal portion is traversed longitudinally by four min- ute, refractive, somewhat beaded longitudinal striae. The pharynx is about as deep as it is wide, and in its widest part is a little more than half as wide as the front of the head. It is well filled at the base with the two cres- cent-shaped, pointed, pharyngeal teeth. These extend inward and then forward, their points being close to the body axis. The front contours of the teeth are incurved, and at one point on their front surface they are exceedingly finely striated. Each of these teeth occupies about one-fourth of the width of the head; measured in the longitudinal direction its ex- treme limits are less than when measured transversely. The entire length of the pharynx is probably somewhat greater than the width of the head, though it joins the lumen of the oesophagus in such an indefinite way that it is sometimes rather difficult to say where the pharynx ceases and the true oesophagus begins. The portion of the oesophagus surrounding the pharynx is, however, distinctly, though slightly, swollen, so that it is proper to speak of an elongated pharyngeal bulb. Just at the base of the phraynx this bulb is two-thirds as wide as the corresponding portion of the head. At a point two or three body diameters farther back it is only about half as wide as the corresponding portion of the neck; thence onward it expands a very little. Near the middle of the neck the oesophagus expands to form the elongated muscular median bulb, which is three-fourths as wide as the middle of the neck. Here the lining is more strongly developed, and occupies about one-fourth of the optical longitudinal section, while the lining of the preceding portion of the oesophagus occupies not more than one-fifth to one- sixth of the diameter. Behind the median bulb the oesophagus is less strongly developed. The lining is much less conspicuous and the radial muscular fibers are less abundant. At first this posterior portion of the oesophagus is only about one-fourth as wide as the middle of the neck. It expands gradually until near the end, then more rapidly so as to form an elongated- clavate swelling, three-fourths as wide as the base of the neck. The lining of this portion of the oesophagus is a distinct feature, but is by no means so strongly developed as that of the preceding portions of the eosophagus. There is a well developed flattish cardia, half as wide as the base of the neck. The intestine, which is separated from the oesophagus by a distinct constriction, becomes at once about three-fourths as wide as the body. Its cells contain scattered, nearly colorless granules of variable size, the largest of which have a diameter nearly equal to the distance between two of the adjacent longitudinal striations. From the slightly depressed anus the rec- tum, which is about one and one-half times as long as the anal body diam- eter, extends inward and forward. The tail is conoid from the anus and tapers rather regularly to the extremely fine, hair-like terminus. There are no caudal glands. From the rather prominently elevated vulva the chitinized vagina leads inward at right angles to the ventral surface half way across the body, where it joins the two symmetrically-placed uteri. The reflexed ovaries reach 44 NORTH AMERICAN about half way back to the vulva and contain six to ten developing ova ar- ranged single file. The thin-shelled eggs, which are deposited before segmentation begins, are fully twice as long as the body is wide and about one-third as wide as long, and occur in the uteri one at a time. Full-grown ova are ellipsoidal, and about one and one-half times as long as the body is wide and about half as wide as long. 55 .9 12.3 15.5 -M 86.6 i.o mm. i.i 1.4 1.4 1.5 1.6 The tail of the male is like that of his mate in form. There are no sup- plementary organs in front of the anus. The special male papillae charac- teristic of this genus are located as follows : A single tapering, ventrally submedian papilla a little in front of the proximal ends of the spicula, and slightly farther back a lateral pre-anal papilla; a ventrally submedian papilla as far behind the anus as that first described is in front of it ; a lateral papilla twice as far behind the anus as that just described ; a ventrally submedian papilla as far behind that just described as the latter is behind the previous post-anal papilla; between the two ventrally submedian papillae just de- scribed a group of minute subventral papillae ; near the middle of the tail, on the slender part, two sublateral papillae. Most of these papillae are slender, tapering, and one-third to one-half as long as the anal body diame- ter. The two equal, yellowish, arcuate, acute spicula are about one and one- fourth times as long as the anal body diameter. They taper pretty regu- larly from near the proximal ends, where they are one-fourth as wide as the corresponding portion of the body. The proximal ends diminish sud- denly in diameter, and are then cephalated by expansion. Each expansion is a rather strongly refractive, more or less bulbous piece of chitin. The acces- sory piece is arcuate and about one-third as long as the spicula. It is par- allel to and applied closely to the spicula. Its framework consists of two distinct, nearly parallel parts. The ejaculatory duct is about one-fourth as wide as the body. The blind end of the single outstretched testicle lies a little farther behind the base of the neck than this latter is behind the an- terior extremity. Habitat: Spring. Washington Country Club, Chevy Chase, Md. Sublimate to balsam. PRISMATOLAIMUS, de Man, 1880. Fig. 4, Plate III. 14 4. Prismatolaimus sternus, n.sp. i.i mm. 1.2 1.5 1.9 1.9 1.5 The moderately thin layers of the transparent, colorless cuticle are tra- versed by about 550 transverse striae, resolvable with high powers into rows of minute elements. There are no longitudinal striations. Scattered on FREE-LIVING FRESH-WATER NEMATODES 45 the neck and body there are a few hairs arranged at right angles to the surface. These generally have a length equal to the width of two to three annules of the cuticle. The cylindroid neck ends in a somewhat truncated head, which is not set off in any way. On the outer margin of the head at the base of the lips there is a circlet of ten widely spreading, straight, taper- ing cephalic setae, two of somewhat unequal size on each submedian line, and one on each lateral line. The longest of these setae are a little more than half as long as the head is wide. For two-thirds of their length they are finger-shaped; the remaining third is a much narrower bristle. The very thin lips are arched over the prismoid pharynx, which is nearly as deep as the head is wide, and about three-fifths as wide as the head. It attains its full width immediately behind the lips, and continues to have the same width to the end, so that the bottom of the pharynx, though not even, ex- tends across the base of the head approximately at right angles to the body axis. Where the lumen of the oesophagus joins the pharynx there is, how- ever, a slight backward extension of the pharyngeal cavity. There are no eye-spots. The amphids occur in the form of somewhat elongated trans- verse markings placed transversely on the neck somewhat farther behind the base of the pharynx than this latter is behind the anterior extremity. Each amphid has a length about one-third as great as the corresponding width of the neck, and is about half as wide as long. Behind each amphid, at a distance equal to the width of two to three annules of the cuticle, there is a short seta. The oesophagus receives the base of the pharynx, and is at once nearly three-fourths as wide as the head. It narrows very slightly in diameter as it passes backward, so that where it passes through the nerve- ring it is about two-thirds as wide as the neck. It continues to have prac- tically the same diameter to near the end, where it is two-thirds as wide as the base of the neck. Immediately in front of the intestine there is a small segment of the oesophagus which is set off by a constriction. This portion is somewhat spheroidal in form. The lining of the oesophagus is a distinct feature throughout its length, and comes into view in the optical section as a single refractive line. This line is nowhere materially altered. There is no distinct cardia, unless the above mentioned spheroidal segment of the oesophagus may be so considered. The rather thick walled intestine, which is set off from the oesophagus by a distinct constriction, becomes at once about two-thirds as wide as the body, and is composed of cells of such a size that probably about four are required to build a circumference. These cells contain numerous granules of rather uniform size, which are not dis- posed so as to give rise to a tessellation. From the somewhat continuous anus the rectum, which is about as long as the anal body diameter, extends inward and forward. The tail end begins to taper from some distance in front of the anus, and tapers regularly thereafter throughout the anterior portion of the tail. The posterior portion tapers very slightly, and has a diameter one to two times as great as the width of one of the annules of the cuticle, measured near the anus. Though the terminus has considerable 46 NORTH AMERICAN width there is no spinneret. The lateral fields are about one-third as wide as the body. The nerve-ring surrounds the oesophagus somewhat squarely. On the dorsal side, a little behind the cardiac constriction there is a body which presses the intestine a little to one side, which may perhaps be the renette cell. This body has a length as great as the corresponding body di- ameter, and is about one-fourth to one-third as wide as long. The vulva is somewhat elevated, and from it the vagina extends inward at right angles to the ventral surface about one-third the distance across the body. There are two symmetrically disposed, reflexed ovaries, the blind ends of which lie near the vulva, the position depending to a considerable extent upon the de- velopment of the much elongated eggs. The ovaries are moved backward and forward to a certain extent in accordance with the stage of develop- ment of the eggs. The eggs, which have been seen in the uteri one at a time, are much elongated four or five times as long as the body is wide and about one-fifth as wide as long. They appear to be deposited before segmentation begins. Habitat: Roadside pool, Douglas Lake, Michigan. Sublimate to balsam. SPILOPHORA, Bastian, 1865. Fig. 5, Plate III. 5. Spilophora canadensis, n.sp. The thin, transparent layers of the colorless, practically naked cuticle are traversed by 750 transverse striae, resolvable with high powers into rows of dots, which at the lateral wings are so modified as to give rise to two distinct longitudinal rows of dots of larger size. Along the middle of the body one of these rows is more pronounced than the other. Opposite the base of the neck the distance between these two longitudinal rows is about four times as great as the distance between two of the dot-like ele- ments. There are no eye-spots, nor have any distinct traces of amphids been seen. If the latter are present they must be very inconspicuous. The lips are so small that it is very difficult to count them, but there appear to be twelve, each one obscurely conical. There are no very marked subdivisions between these lips, so that the shallow cyathiform anterior portion of the pharynx, (a, Fig. 5) which is about half as wide as the head and about one-third to one-half as deep as wide, is not prominently striated radially as is some- times the case in this and related genera. From the slightly depressed vulva, the vagina leads inward at right angles to the ventral surface about half way across the body, where it joins the two symmetrically-placed uteri. The re- flexed ovaries reach fully half way back to the vulva, at least in young speci- mens such as have been examined, and contain a dozen to twenty developing ova arranged in more or less double file. The eggs appear to be elongated, somewhat longer than the body is wide and about one-third as wide as long. It is possible, however, that there is some error here as the description is FREE-LIVING FRESH-WATER NEMATODES 47 derived from a single specimen in which these features are rather obscure. The reversal in the striations of the cuticle is plainly to be seen in the re- gion of the vulva, and its location is indicated by a slight rise in the contour. This slight elevation extends also to the subcuticle. 60 .5 8.3 14.8 -M 88.4 .7 mm. 2. 4.3 4.7 5. 3.2 The wing markings on the anterior part of the tail are pronounced, but on the posterior part much less so. A little in front of the anus they are as pronounced as they are at the base of the neck, and both are equally visible, and the structure not infrequently re- sembles that of a ladder with the rungs placed close together, just as it does on the neck. The lateral fields appear to be about one-third as wide as the body. Near the middle of the body may plainly be seen the location where the cuticle reverses its structure. Although the striations are minute they present the same character as in species where the striations are coarse, and, upon careful examination, can be seen to be retrorse in opposite directions on the two halves of the body. Habitat : Fresh water ponds, Cape Breton Island, Dominion of Canada. MICROLAIMUS, de Man, 1880. Fig. 6, Plate III. 27 6. Microlaimus fluviatilis, n.sp. *- 6 8 -5 *5-5 V 85. mm 1-9 3-5 4-3 47 2.6 The thin layers of the transparent, colorless, naked cuticle are traversed by exceedingly fine transverse striae, which are resolvable with great diffi- culty into rows of dots, and are not modified on the lateral fields. The conoid neck ends in a rounded head set off by an almost imperceptible con- striction. On the outer margin of the head there is a circlet of four sub- median, slightly tapering cephalic setae, each about one-third as long as the head is wide. The vestibule is considerably shorter than any of the cephalic setae, and is longitudinally striated, indicating, no doubt, that the lips can be opened outward in receiving food. These longitudinal striations of the vestibule are too minute to be counted, but there are apparently about twelve. The circular amphids are about one-fourth as wide as the corresponding portion of the head, and are located at a distance from the anterior ex- tremity equal to one and one-half times the diameter of the front of the head. There are no eye-spots. The limits of the pharynx are indicated by a slight constriction in the oesophagus. The base of the pharynx is some- what more than halfway back to the amphids. The general form of the pharynx is cylindroid or prismoid. It is armed with minute and very in- conspicuous, somewhat inward pointing and apparently not very regular teeth or projections. The most conspicuous of these projections are two just behind the base of the lips, one dorsal and the other apparently ventral, and 48 NORTH AMERICAN a third at the base of the pharynx on the dorsal side. The oesophagus be- gins as a tube about half as wide as the corresponding portion of the neck, and continues to have this diameter until it swells to form the pyriform cardiac bulb, which is about three-fourths as wide as the base of the neck, and contains a distinct chitinized threefold, rather simple, valvular apparatus, occupying two-fifths of the diameter as seen in longitudinal section. The musculature of the bulb is divided into three sections, a small anterior sec- tion, a middle and a posterior section. Of these two latter the posterior is slightly the smaller. The lining of the oesophagus is a fairly distinct feature throughout its length. There is no very distinct cardia. The intestine joins the middle of the posterior surface of the cardiac bulb, and is there one- fourth as wide as the base of the neck. It soon expands so as to become about two-thirds as wide as the body. It is rather thick walled, and is com- posed of rather thick cells which are of such a size that about four are re- quired to build a circumference. These cells contain minute granules. From the anus the rectum, which is considerably longer than the anal body diam- eter, extends inward and forward. The tail is conoid, and tapers from the anus toward the terminus, which is conoid and has a diameter one-third as great as that of the base of the tail, and bears a blunt convex-conoid unarmed spinneret. The rather small caudal glands appear to be located in the an- terior third of the tail. The lateral fields have not been seen. From the inconspicuous vulva the vagina leads inward at right angles to the ventral surface to the single or double uterus, which when single extends forward. There sometimes appears to be a small posterior rudimentary branch to the sexual organs, which is about equal in length to the corresponding body diameter. The reflexed ovary reaches about halfway back to the vulva, and contains about half a dozen or more ova arranged somewhat irregu- larly. The eggs appear in the uterus one at a time. They are smooth, some- what thin-shelled, and are about twice as long as the body is wide, and about one-third as wide as long. They appear to be deposited before segmentation begins. Specimens with one ovary, and those with two, appear to be about equally numerous ; as no other difference has been detected, they are in- cluded for the present under the same name and description. The renette cell is an elongated cell located a short distance behind the base of the neck. It is fully as long as the body is wide, and about one-fourth as wide as the body. The excretory pore appears to be located opposite the nerve-ring. The nerve-ring surrounds the oesophagus somewhat squarely. Habitat: Maple River, Michigan. Sublimate to balsam. TRIPYLA, Bastian, 1865. Fig. 7, Plate III. 49, --,.,, LI 6.8 19.6 '54' 83.5 7. Tnpyla lata, n.sp. 2.4 mm. 2.3 3-1 3-5 4- 3-2 The thick layers of the transparent, colorless, naked cuticle are apparently traversed by about 250 transverse striae, which are not further re- FREE-LIVING FRESH-WATER NF.MATODES 49 solvable. In the lumen of the pharynx at a point removed from the anterior extremity a distance a little greater than the radius of the head, there is a minute inward-pointing dorsal tooth, having a length about equal to the width of one of the annules of the cuticle. This and other matters prove that the pharynx, although not readily dis- tinguished, extends backward a distance about equal to the width of the head. In some specimens it is possible to see a distinct transverse fold in the lining of the oesophageal tube. This is located at a dis- tance from the anterior extremity about equal to the corresponding diameter of the head, and undoubtedly indicates the posterior lim- its of the pharynx. It is possible that the tooth just mentioned may be con- nected with internal glandular structures in the oesophagus, as the interior of the dorsal segment of the oesophagus at this point is usually more or less different in structure from the other portions and does not seem to be made up entirely of muscular fibers. The oesophagus is separated from the intestine by a flattish, pseudo-bulb. The bulb is separated from the oesopha- gus on one side and the intestine on the other by deep and distinct constric- tions. In the anterior constriction there are at least two granular, elongated cells of considerable size. The nerve-ring surrounds the oesophagus rather squarely. Nothing definite is known concerning the renette or the excretory pore. From the inconspicuous vulva, the vagina leads inward at right angles to the ventral surface fully half way across the body, where it joins the two symmetrically-placed uteri. The reflexed ovaries reach about half way back to the vulva, and contain a dozen to twenty developing ova ar- ranged somewhat irregularly. Both in front of and behind the vulva there are unicellular glands, having a diameter about one-sixth as great as that of the body. 50 .7 6.8 19.3 -M- 82.8 2.4 mm. 2.1 3.2 3.9 4.8 4.1 The tail of the male is like that of the female except that the anus is slightly raised. In front of the anus there is a ventral row of about twenty innervated supplementary organs, reaching to near the head. The distance between two consecutive organs is about equal to the ra- dius of the body. Each of these appears to consist of a nerve-ending which penetrates the cuticle and forms a papilla, around which there is an almost imperceptible elevation having a width about equal to two of the annules of the cuticle. The visibility of this small organ is quite as much due to the alteration in the body wall and subcuticle as to that in the cuticle. There are no supplementary setae or papillae either in front of the anus or behind it. The two equal, slightly arcuate, uni- formly tapering, acute spicula are about one and one-fourth times as long as the anal body diameter. Their proximal ends are not cephal- ated, though the wall of the cuticle is very slightly thickened at that point. The spicula taper regularly from the proximal ends to the rather 50 NORTH AMERICAN truncated points. There are obscure accessory pieces lying close to the surface of the spicula and forming a double groove in which these lat- ter slide. The ejaculatory duct, though narrow at first, soon becomes nearly half as wide as the body. There are two slender, outstretched testicles extending in opposite directions from near the middle of the body. The anterior one has its blind end about as far behind the base of the neck as the nerve-ring is in front of it. Habitat : Alpine lakes, Bald Mountain, Colorado. Formalin to glycerine. TERATOCEPHALUS, de Man, 1876. Fig. 8, Plate IV. ii 8. Teratocephalus cornutus, n.sp. : : '- : .8 mm. i.i i.o 1.8 1.9 i.i The thin, transparent layers of the colorless naked cuticle are traversed by about 1500 transverse striae, resolvable into rows of minute dots, which are modified on the lateral fields. These modifications have been seen in all parts of the body, and near the tail consist of two to three irregular longitudinal rows of enlarged dots. The posterior portion of the neck ta- pers but little. The anterior portion becomes convex-conoid toward the head, which bears a lip region more or less set off by a constriction opposite the base of the spreading cephalic setae, which are four in number and submedian in position. Each seta is a little more than half as long as the head. These are connected with a refractive six-ribbed chitinous dome-like framework, which extends back to opposite the middle of the pharynx. The ribs start at the lip region, extend backward, and then join each other oppo- site the base of the vestibule. The chitinous refractive elements at this latter region form a rather distinctly crenate contour around the head. No other setae than the cephalic setae have been seen in any part of the body. The lips appear to be rather thin, and are arched together over the unarmed pharynx, which is somewhat elongated and about half as wide as the base of the head. While it is somewhat irregular in form it is approximately prismoidal or cylindroid and nearly as deep as the head is wide. Its walls are not very strongly chitinized, but more strongly so anteriorly than posteriorly. The oesophagus receives the base of the pharynx, and soon becomes half as wide as the base of the head. In the anterior portion of the oesophagus, a short distance , behind the pharynx are three slightly arcuate, refractive elements, corre- sponding somewhat in curvature with the contour of the front end of the oesophagus. These resemble to a certain extent the refractive ele- ments in the posterior chamber of the pharynx of Plectus. In the present species they are about as long as the pharynx, and are separated a dis- tance about equal to one body width. They are a little wider and more plainly visible anteriorly than posteriorly. The obscure amphids, as FREE-LIVING FRESH-WATER NEMATODES 51 far behind the base of the pharynx as this latter is behind the anterior extremity, are one third as wide as the corresponding part of the head, and consist of obscure spirals of one wind. There are no eye-spots. The oesophagus begins as a tube about half as wide as the correspond- ing portion of the head, but expands very slightly as it passes back- ward, so that at the middle it is about two-thirds as wide as the middle of the neck. Behind this point it diminishes. There is a break in the musculature somewhat similar to that occurring in Cephalobus. At the break, which occurs at the beginning of the fourth fifth, the oesophagus is somewhat narrow, about half as wide as the corre- sponding portion of the neck. It finally expands to form the ellipsoidal cardiac bulb, which has a relatively large, chitinous, striated, complicated, three-fold valvular apparatus half as wide as itself. There is a truncate- conoid cardia about one-third as wide as the base of the neck. The lining of the oesophagus is a fairly distinct feature. The thick-walled intestine, which is separated from the oesophagus by a constriction, soon becomes two- thirds as wide as the body. It is composed of cells of such a size that four are required to build a circumference. The walls of these cells are refrac- tive, so that the cells are readily distinguished from each other, though there is no distinct tessellation. These cells contain minute very uniform granules. The lining of the intestine is refractive, so that the lumen is distinctly to be seen. From the rather inconspicuous anus the rectum, which is about as long as the anal body diameter, extends inward and forward. The internal sexual organs are double and symmetrically reflexed. The tail is conoid from the anus to the subacute terminus. This species is related to those described by Dr. de Man under the name of Teratocephalus. It is doubtful whether these forms will not have to be subdivided at some future time, after the accumulation of the necessary data. Habitat: Maple River, Michigan. Sublimate to balsam. ALAIMUS, de Man, 1880. Fig. 9, Plate IV. .2 ii. 19- 35- 92. 9. Alaimus simplex, n.sp. .3 .8 .9 i.i -6 The thin, transparent layers of the colorless, naked cuticle would ordi- narily be described as destitute of striations. Very minute striations may be observed in the subcuticle at the extremities, when the specimens are ex- amined under favorable conditions with the highest powers. There are obscure traces of lateral wings. The conoid neck ends in a rounded head not set off in any way. There are no distinct lips, and only the faintest possible indications of labial papillae. These are so obscure that it has been found impossible to enumerate them. There is no pharynx and the mouth opening is exceedingly minute. No amphids or eye-spots have been seen. 52 NORTH AMERICAN The oesophagus begins at the lip region as a tube two-thirds as wide as the head, and expands gradually and rather regularly to the end, where it has a diameter three-fourths as great as that of the neck. A short distance be- hind the head end, a distance six times as great as the diameter of the head, there is a slight alteration in the structure of the oesophagus the significance of which remains doubtful. The lining of the oesohpagus is not a very dis- tinct feature. There is a very obscure, small cardia. The intestine, which is separated from the oesophagus by a constriction, becomes at once about two-thirds to three-fourths as wide as the body. At first its cells contain but few scattered granules, but soon they are characterized by the presence in them of loosely scattered yellowish-brown granules of variable size, the largest of which have a diameter nearly one-eighth as great as that of the body itself, and the smallest of which are very much smaller. These are not arranged so as to give rise to any distinct tessellation. Toward the end of the intestine the granules again become less abundant and smaller, so that for some distance in front of the rectum there is only here and there a granule. From the depressed and conspicuous anus the chitinized rec- tum, which is a little longer than the anal body diameter, extends inward and forward. There is no distinct pre-rectum. The tail end begins to taper from a long distance in front of the anus, but tapers very gradually to behind the anus. Thence onward it is inclined to be arcuate and tapers regularly to near the terminus. Near the end it tapers more rapidly than elsewhere, and finally comes to an almost acute point at the terminus. A short distance in front of the terminus, however, the diameter is about half as great as it is at the anus. There does not appear to be any spinneret, and therefore, of course, caudal glands are absent. The lateral fields appear to be about one-third as wide as the body. Nothing is known concerning the excretory pore. From the slightly elevated vulva the vagina leads inward nearly at right angles to the surface more than halfway across the body, where it joins the single uterus, which extends backward. The ovary is reflexed, and the blind end is about halfway back to the vulva. The eggs occur in the uterus one or two at a time, and are very much elongated. They are about six times as long as the body is wide, and about one-eighth as wide as long, and are covered by a distinct, smooth shell. They are apparently deposited before segmentation begins. The spermatozoa appear to be elon- gated-ellipsoidal, and a little more pointed at one end than at the other. They have a length one-fifth that of the body diameter. 68 2 . 3 mm. 3 -6 .7 .9 .7 The tail of the male is like that of the female in form and size, but the anus is somewhat elevated. In front of the anus there appears to be a ventral row of very obscure, broad, flattish supplementary organs. Perhaps these ought to be described as locations of nerve endings rather than as distinct organs. Their number remains doubtful, but there are about FREE-LIVING FRESH-WATER NEMATODES 53 three or four occupying a distance equal to half the length of the tail. The two equal, straight spicula are rather obscure. Their length is no greater than the length of the anal body diameter. Oblique copulatory muscles are seen in the vicinity of the spicula, and there is a refrac- tive element passing backward from the accessory piece toward the ventral side of the tail near the anus, which may be muscular, or possibly chitinous and serving for the attachment of muscles. The ejaculatory duct is about one-third as wide as the body, the vas def- erens somewhat wider. Whether there are two testes or only one has not been determined. There is a broad, rounded, blunt end of a testis located as far behind the base of the neck as this latter is behind the anterior extremity. Habitat: Big Lake, Fla. Bouin solution to glycerine. PLECTUS, Bastian, 1865. Fig. 10, Plate IV. 35 2. 10.7 IQ. '49' 92.6 10. Plectus tubifer, n.sp. .74 mm. 2.1 34 3-5 3-2 2.3 The skin is of medium thickness, colorless, and traversed transversely by fine, plain striae. The striae are of such a size that about twenty of them occupy a space equivalent to the body diameter. There are no hairs on* the surface of the body, but throughout the length of the body, more particularly on the submedian lines, may be seen very faint markings in the cuticle, which indicate the location of four rows of pores connecting with interior organs. Immediately behind the lateral organs one sees the first of the series of pores located in the lateral line. This first pore, though much smaller than the lateral organs, is yet somewhat larger than the succeeding ones, which grad- ually spread out to form two submedian rows. The total number of these pores on one side (of the male) is about one hundred; that is, there are about two hundred in all. The six low, rounded lips are rather massive, and are arched together over the pharynx. These lips appear to be armed with chitinous processes on the inner surface, these processes surrounding a short napiform vestibule leading to the pharynx proper. If any labial papillae are present they are exceedingly minute ; what appear to be traces of papillae may occasionally be seen. The lateral organs are well forward, being lo- cated only slightly behind the cephalic setae. They present transversely elongated contour markings open on the posterior margin. The lateral fields appear to attain a considerable width and two chitinous, lateral markings close together with a third between them, appear to indicate the existence of a wing on each side of the body. 54 NORTH AMERICAN 54 1.9 10.1 19.2 '-M 91.5 79 mm 2. 3-1 34 3-6 3-3 2.4 10. 19.5 '-M 93. 3-2 3-3 possessed four supplementary organs, the additional one being some little distance in front of the others, which were arranged as illustrated. Sometimes there are only two of these organs, one smaller than the other. The cuticle of the ventral surface is slightly thickened and elevated where it is pierced by these tubular organs, which appear in some instances to be slightly exserted. Apart from these preanal supplementary organs, there are ventrally submedian papillae on the tail ; one pair near the middle, an- other pair half way between these and the anus, and a third pair part way from that first mentioned to the terminus. There is a fourth pair indistinctly to be seen just behind the anus; these are closer together than the members of the other pairs. Furthermore there are one or two very small pairs near the terminus, but perhaps these may partake more of the nature of hairs than of papillae. Just in front of the anus there is a single ventral almost setose papilla. There occur in front of the anus at least two pairs of ven- trally submedian papillae. These are located one just in front of the pos- terior supplementary organ and the other just behind it. Most of these features are not easy to decipher, very careful observation being necessary to enumerate the papillae as above. There are two testicles, one anterior to the other, the anterior being outstretched and extending forward, the pos- terior being reflexed near its middle, so that its blind end lies somewhere near the junction of the two. The anterior one of this pair is connected with the seminal vesicle by a tubular portion, which lies alongside the re- flexed posterior member. Habitat: Arlington, Va. Flemming solution to glycerine. DORYLAIMUS, Dujardin, 1845. Fig. 12, Plate V. 43 11. Dorylaimus fecundus, n.sp. : '- 3.4 mm. .5 i.i 1.6 1.9 1.2 The thin layers of the transparent, colorless, naked cuticle are traversed by exceedingly fine, plain, transverse striations resolvable with the highest powers of the microscope under favorable conditions. Longitudinal striations are visible throughout the length of the body. The presence of amphids is indicated by a transverse marking immediately behind the lip region, and somewhat in front of the guiding ring of the spear. The anterior contour of each organ is a transverse line about three-fifths as long as the corre- sponding portion of the head is wide. Extending backward from this are lateral contours which approach each other slightly and end indefinitely. The FREE-LIVING FRESH-WATER NEMATODES 55 oesophagus begins as a tube about half as wide as the corresponding portion of the neck, and continues to have this diameter until near the middle of the neck, where it first begins to expand. A little behind the middle of the neck it expands rather suddenly, so that the remainder of the organ is about two-thirds as wide as the base of the neck. There is a much elongated conoid cardia nearly as long as the body is wide. The intestine, which be- comes at once three-fourths as wide as the body, is separated from the oesophagus by a distinct though slight constriction. The cells forming the intestine are of such a size that about four or five are required to build a circumference. They contain granules of variable size, the larger of which have a diameter equal to the thickness of the outer transparent cuticle, and the smaller a diameter only about one-fourth as great as that of the larger. These granules are so arranged as to give rise to a very obscure tesselation. The pre-rectum is about three to four times as long as the corresponding body diameter, and is separated from the intestine by a difference in struc- ture, the granules contained in its cells being smaller, and not darkening un- der the influence of osmic acid, as do those of the intestine. Nothing is known concerning the salivary glands or the renette. The longitudinal fields are well developed, being about half as wide as the body. The nerve-ring surrounds the oesophagus somewhat obliquely. Each of the two elongated uteri may contain three to five eggs at a time. These, as they appear in the uteri, are elongated, finely granular, rather thin-shelled, and about one and one-half times as long as the body is wide, and about half as wide as long. The shells are flexible, so that owing to the pressure of one egg on another in the uterus the surfaces are often indented. 3-5 mm. .6 1.2 1.4 1.4 1.4 In addition to the ventral row of supplementary male organs shown in the illustration, there are two rows of ventrally submedian, innervated papil- lae, arranged in a somewhat equidistant manner. Where these reach the surface of the body they give rise to almost imperceptible elevations which, however, are of a different character from those at the ends of the ventral organ shown in p, Fig. 12. In other words, these papillae are more nearly the homologues of the ordinary tactile hairs or papillae so common on the sur- face of nematode worms. These submedian papillae are located at a distance from each other equal to about two-thirds the body diameter. They are very nearly coextensive with the oblique copulatory muscles. Habitat: Algae, Potomac River, Washington, D. C, 1911. Flem- ming solution to glycerine. 56 NORTH AMERICAN IRONUS, Bastian, 1865. Fig. 13, Plate V. 30 12. Ironus americanus, n.sp. : : 2.3 mm. 1.6 2.3 2.7 2.9 1.3 The moderately thin layers of the transparent, colorless, naked cuticle appear to be destitute of striations. There are three somewhat conoid lips, which when open, give to the head a somewhat truncated appearance, when folded a somewhat rounded appearance. Each lip bears internally a slightly arcuate, conical tooth, whose altitude is somewhat greater than the width of its base. When the mouth is so opened that the apices of these refractive teeth are about on a level with the anterior extremity their bases lie a little in front of the bases of the cephalic setae. The apices of these teeth are slightly blunt and they have a slight outward curvature. The walls of the pharynx are strongly refractive, and have about the same thickness as the walls of the cuticle. The chitin of the walls of the pharynx, however, is more refractive than that of the cuticle. In this respect it resembles the chitin of which the teeth are composed. Except for the teeth at the mouth opening the pharynx is unarmed, but presents on the dorsal side about half way between the head and its posterior extremity three or four exceedingly minute projections with corresponding depressions. The oesophagus begins near the base of the pharynx, at least it is at this point that the radial struc- ture becomes pronounced. At first it is about two-thirds as wide as the cor- responding portion of the neck. It enlarges a little and very gradually, so that finally it is about half as wide as the base of the neck. The lining of the oesophagus is an exceedingly distinct feature throughout its length. It gen- erally has the appearance of three refractive lines occupying a space nearly one-fourth as wide as the oesophagus itself. There is a large cylindroid or hemispherical cardia, one-third as wide as the base of the neck. The in- testine, which is separated from the oesophagus by a deep, narrow and dis- tinct constriction, becomes at once about three-fifths as wide as the body. Its cells contain scattered granules of variable size, the largest of which have a diameter nearly equal to the width of the refractive portion of the lining of the oesophagus, and the smallest of which have a diameter not more than one-tenth as great. The body wall is thick, generally occupying about three- fifths of the diameter of the body. The lateral fields are a little more than one-third as wide as the body. Nothing is known concerning the renette or the excretory pore. There is no spinneret. The tail, nevertheless, con- tains small cells near the anus which bear a certain resemblance to the ordi- nary caudal glands. From the slightly elevated vulva, the vagina leads in- ward at right angles to the ventral surface half way across the body where it joins the two symmetrically-placed uteri. The reflexed ovaries reach three-fourths the distance back to the vulva, at least in specimens which do not contain eggs. The ovaries contain about a dozen ova arranged for the FREE-LIVING FRESH-WATER NEMATODES 57 most part single file. Nothing very definite is known concerning the form and size of the eggs, but from the size of the apparently matured ova it is assumed that the eggs are considerably elongated, perhaps two to two and one-half times as long as the body is wide, and if so, it is unlikely that more than one is contained in the uterus at a time. Habitat: Deer Bottom, Pikes Peak region, Colorado. Formalin to glycerine. ONCHOLAIMUS, Dujardin, 1845. Fig. 14, Plate V. 13. Oncholaimus punctatus, n.sp. The rather thin., transparent, colorless layers of the naked cuticle appear to be destitute of striations. It is rather difficult to observe the cuticle on account of the presence in it of numerous dot-like elements, which near the head are arranged in longitudinal groups, of which the widest is the lateral group. The longitudinal arrangement of the granules, is continuous through- out the body, but it is most marked on the lateral fields where there is a definite band of them, having a width about two-fifths as great as the width of the body. Each margin of this band is made up of a distinct longitudinal row of granules arranged single file. The neck is slightly conoid, becoming slightly convex-conoid toward the rounded head, which is not set off in any way, or at most by an exceedingly obscure, broad constriction opposite the pharynx. The six lips are distinct and well developed and have a distinct, somewhat chitinous framework. They are arched together over the pharynx in such a way as to produce a dome-like effect, the very thin and movable flaps at the ends of the lips meeting together at the middle of the front of the head. Opposite the middle of the amphids there is a transverse marking or line which extends around the middle of the head. It is characterized by staining somewhat more strongly with carmine than the other portions of the cuticle. There are no eye-spots. The oesophagus begins at the base of the pharynx with a diameter three-fourths as great as that of the base of the head, and it continues to have this diameter until some distance behind the nerve-ring. It then begins to expand gradually, so that finally it is about three-fourths to four-fifths as wide as the base of the neck. The lining is a distinct feature throughout the length of the oesophagus. There is a dis- tinct conoid cardia, whose base is about half as wide as the corresponding portion of the body. The intestine, which is separated from the oesophagus by a deep and distinct constriction, appears to have rather thin walls and to be composed of cells of such a size that probably six or more would be re- quired to build a circumference. These cells contain numerous granules of rather uniform size. The lateral fields are about two-fifths as wide as the body. The loca- tion of the ventral gland has not been made out. The excretory pore is lo- 58 NORTH AMERICAN cated just behind the base of the pharynx. The duct which leads to it seems to be destitute of an ampulla. 40 1.9 10.2 21.4 -M- 92. _ - 2.1 mm. 1.2 2.2 2.8 2.5 1.8 In front of the anus there is a series of about fifty pairs of oblique copulatory muscles, whose presence is indicated by the oblique groups of granules in the cuticle. The ejaculatory duct is about one-third as wide as the body. The blind end of the anterior testicle is about twice as far behind the base of the neck as this latter is behind the anterior extremity. Habitat : Fresh water ponds, Cape Breton Island, Dominion of Canada. Sublimate to balsam. DOLICHODORUS, n.g. Fig. 16, Plate VI. 58 14. Dolichodorus heterocephalus, n.sp.' 3 (34) 7 '* 9 '* ' 52 ' 97 ' 2 3. mm. .6 (i.i) 1.6 1.7 2.1 1.2 The thin layers of the transparent, naked, colorless cuticle are traversed by transverse striae resolvable with high powers under favorable conditions into rows of exceedingly minute, somewhat irregular elements. This reso- lution is not at all difficult in specimens which are moulting. Under these conditions scales of the outer cuticle sometimes survive, readily resolvable into refractive transverse markings between which are the small elements mentioned. Ordinarily at first glance, the cuticle appears to be merely re- solvable into transverse striae which are somewhat roughened on the edges of the dividing lines. The conoid neck ends in a head which has a very prominent lip-region set off by a very prominent and deep constriction. The front of the head is rounded, and the constriction separating the lip-region from the remainder of the head is of such a nature that the contour of the lip-region, when seen in optical longitudinal section is somewhat elliptical, so that the lip-region has the form of an ellipsoid of rotation. The depth of this figure is about equal to half its width. No papillae have been seen on the lips, but minute papillae might readily be present without having been observed. No traces of amphids have been seen. There are no eye-spots. The vestibule is exceedingly narrow and closely surrounds the apex of the very slender narrow spear. This latter extends nearly half-way to the an- terior border of the median bulb and is long and slender like that of Trichodorus. The oesophagus at the base of the spear is a tube about one- third as wide as the corresponding portion of the neck, and continues to have this diameter until it expands suddenly to form the elongated median bulb, which is three-fourths as wide as the corresponding portion of the neck and fully twice as long as wide and is armed internally with a conspicuous, ellip- soidal, rather simple valvular apparatus nearly half as wide as itself. When FREE-LIVING FRESH-WATER NEMATODES 59 seen in optical longitudinal section the bulb is a little wider posteriorly than anteriorly, so that its sides are not parallel, but approach each other a trifle as they pass forward. The bulb ends more abruptly posteriorly than an- teriorly, and is continued by a narrow section of the oesophagus only one- eighth as wide as the corresponding portion of the neck and about as long as the corresponding portion of the neck is wide. This is succeeded by a broadly clavate swelling which does not have any distinct chitinous lining, and is of granular structure, rather than muscular. This swelling is about two-thirds as wide as the base of the neck. The lining of the oesophagus is a fairly distinct feature in all parts in front of the posterior swelling. The intestine joins the middle of the rounded surface of the posterior oeso- phageal swelling and is at this point only one-tenth to one-eighth as wide as the corresponding portion of the body, but soon expands to be two-fifths as wide as the body. It is, therefore, relatively narrow. On the other hand, the body walls are correspondingly thick. Nothing is known concerning the renette cell. It is probable that there is an excretory pore located near the nerve-ring. 60 .3 (2.3) 7.9 10.9 -M 99.3 2.4 mm. .4 ( .8) 1.2 1.4 1.7 1.8 The tail of the male is conoid and extends beyond the anus a distance hardly as great as the length of the anal body diameter. It seems likely that the tail is also flattish. When seen dorso-ventrally it appears to be about one- half as long as the spicula, and ends in a dentate terminus one-third as wide as the base of the tail. The cuticle of the tail is very thick, and at first sight seems rather closely to resemble the structure of the two bursal flaps. The distinctly two-parted bursa springs from opposite the middle of the spicula and extends backward and is completely furcated at a point about opposite the base of the tail. The flaps extend backward beyond the terminus of the tail and give to the posterior extremity somewhat the appear- ance of ending in three thin transparent, colorless flaps, one of which is soon seen to be the true caudal extension. The flaps of the bursa are striated in much the same manner as the cuticle, and the margins of the flaps are distinctly thickened. No distinct ribs have been seen in the two broad backward pointing flaps of the bursa. The two equal, rather strongly built, tapering spicula have a length about one and one-half times as great as that of the diameter measured opposite their proximal ends. They are accom- panied by a rather simple accessory piece one-half as long as themselves, judging from its appearance when seen dorso-ventrally. The proximal ends of the spicula can hardly be said to be cephalated, but they are obliquely trancated and wider than elsewhere. When seen dorso-ventrally this width appears to be one-fourth as great as that of the corresponding portion of the body. No special setae are present and no special papillae have been seen. The single outstretched testicle extends forward and has its blind end located about three to four times as far behind the base of the neck 60 NORTH AMERICAN as this latter is behind the anterior extremity. Near its blind end its diam- eter is about one-half as great as that of the body. The spermatozoa art small and numerous and it appears that the reduction divisions take place in a short segment of the testis not far from the blind end. Habitat: Freshwater, Douglas Lake, Michigan. Silver Spring, Florida. Female, Flemming solution to glycerine; from Florida. Male, from Michi- gan, sublimate to balsam. CYATHOLAIMUS, Bastian, 1865. Fig. 17, Plate VI. 26. 15. Cyatholaimus truncatus, n.sp. : : 1.6 mm. 1.8 2. 2.1 3.3 2.1 The moderately thick layers of the transparent, colorless, naked cuticle are traversed by about fifteen hundred transverse striae, resolvable into transverse rows of distinct dots, which are not very materially modified in the lateral fields. The slightly conoid neck ends in a truncated head, whose lip region is set off by an almost imperceptible expansion. The cuticle be- comes somewhat thicker toward the head, and the dotlike markings more distinct and refractive. Beginning near the head and ending near the spin- neret there are circular markings arranged in somewhat irregular rows along the lateral fields. The longitudinal distance between these markings near the middle of the body is a little greater than the radius of the body, and the diameter of the circles is somewhat greater than the width of one of the annules, sometimes twice as great. These markings are not all of the same size, some being nearly twice as large as others.* The lip region is twelve-parted, and there are twelve longitudinal chitinous structures sur- rounding the vestibule. These no doubt indicate the infolding of the lips when closed. Probably the best conception of the lip region is expressed by saying that there are six lips, each two-parted, but that the divisions are all very similar to each other. On the front of the lips there are six forward pointing innervated papillae arranged in the usual position. Along the outer margin of the head there are ten acute, tapering, cephalic setae, two lateral, and four submedian pairs. The longest of these setae are about equal to the radius of the head. According to the position of the lips these setae vary in attitude. They may be folded together on the front of the head so as to be in the position of the spokes of a wheel, but they may point forward when the mouth is partly open, and are in a somewhat spreading position when the mouth is wide open. The pharynx is on the whole con- oid, and about three-fourths as deep as the head is wide. Springing from a little behind its middle is a strong, conical, acute, forward pointing dorsal tooth, the ventral contour of which lies approximately in the axis of the *The two most pronounced rows are nearly opposite the edges of the lateral fields, but there is an irregular median row. FREE-LIVING FRESH-WATER NEMATODES 6l head. Surrounding the pharynx the muscles are somewhat more powerful than in the oesophagus immediately behind, so that there is a very faint pharyngeal bulb. The oesophagus is at first about two-thirds as wide as the corresponding portion of the neck, but gradually enlarges after passing through the nerve-ring, so that finally it is two-thirds as wide as the base of the neck. The lining of the oesophagus is a distinct feature throughout its length. There is no very distinct cardia. There are no eye-spots. The amphids, which are about one-third as wide as the head, are spirals of about two and one-half winds, and are placed opposite the apex of the dorsal tooth. The intestine, which is separated from the oesophagus by a distinct constriction, is at first one-half to two-thirds as wide as the body, but in the greater part of its length is about two-thirds as wide as the body. It is thick walled, and is composed of cells of such a size that comparatively few are required to build a circumference, probably about six. The cells con- tain rather numerous, conspicuous, brownish granules of variable size, the largest of which have a diameter about equal to double the width of one of the annules of the cuticle, the smallest of which are very much smaller. These granules are arranged irregularly, and can hardly be said to suggest any tessellation. From the broad, raised anus the rectum, which is refractive and nearly as long as the anal body diameter, extends inward and forward. The tail is conoid to the subacute conoid spinneret, which has a diameter about one-eighth to one-tenth as great as that of the base of the tail. There do not appear to be any caudal setae. The lateral fields appear to be fully one-third as wide as the body. The nerve-ring surrounds the oesophagus somewhat obliquely. The excretory pore appears to be situated at a distance from the anterior extremity about two and one-half times as great as the width of the head. The renette cell appears to be small and located some distance behind the base of the neck. From the elevated vulva the vagina leads inward at right angles to the ventral surface about half way across the body, where it joins the two-parted uterus. The reflexed, tapering ovaries reach about two-thirds the way back to the vulva, and contain a dozen or more developing ova arranged somewhat irregularly, especially toward the blind end. The rather thin shelled ovate to ellipsoidal eggs are a little longer than the body is wide, and about two-thirds as wide as long. They have been seen to occur in each uterus one at a time, and are appar- ently deposited before segmentation begins. 59- 1.7 6.6 15. -M 91. _ I 1.6 mm. 1.6 2.2 2.3 2.3 2.6 The tail of the male is like that of the female in form and size, but the anus is more prominently elevated. There is a row of four small pre-anal, ventral, tubular, protrudable supplementary organs. The final one of these is opposite the middle of the spicula ; the penultimate nearly opposite the proximal ends of the spicula. The foremost is about three times as far from the anus as the penultimate. From this it will be seen that the organs 62 NORTH AMERICAN are slightly more nearly approximated to each other posteriorly. These organs are not conspicuous features, and scarcely disturb the ventral con- tour. It is possible that each is connected with a unicellular glandular struc- ture nearby. The two equal, tapering, somewhat arcuate spicula are one and one-third times as long as the anal body diameter. Their proximal ends are cephalated by expansion. The accessory pieces alongside are four-fifths as long as the spicula, and somewhat broader than the spicula. In their widest part they are one-sixth as wide as the corresponding portion of the body. They are of rather uniform width throughout. There is a slight constriction near each end, and the distal extremity appears to be very minutely dentate. The spicula are about half as wide as the accessory pieces. The ejaculatory duct is two-thirds as wide as the corresponding portion of the body, as is also the testis. The blind end is as far behind the base of the neck as this latter is behind the anterior extremity. Habitat: Silver Springs, Fla. Flemming solution to glycerine. ETHMOLAIMUS, de Man, 1880. Fig. 19, Plate VII. 27 16. Ethmolaimus americanus, n.sp. '- - : .6 mm. 2.4 3.4 3.9 5.6 2.1 The thin, transparent layers of the practically naked cuticle are tra- versed by very fine transverse striae, resolvable with high powers into rows of closely set dots, which are not modified on the lateral fields. Near the head the dots are a little coarser than elsewhere on the anterior portion of the body. On the tail the dots are much farther apart and, though really arranged in transverse rows, at first glance appear to be scattered irreg- ularly. The conoid neck ends in a somewhat truncated head, which bears on its outer margin a circlet of four slender, spreading submedian cephalic setae, each about half as long as the head is wide. There appear to be twelve minute papillae in the lip region, which when folded together forms a rather small, cyathiform cavity, in the midst of which stands the thumb- shaped, forward-pointing dorsal tooth. This tooth is attached to a dis- tinctly thickened rib of chitin, which extends from the lip region back to the base of the pharynx, and is thicker anteriorly than it is posteriorly. This thickened dorsal rib causes the pharynx to appear somewhat more strongly built on the dorsal side than on the ventral side. The tooth tapers slightly to a blunt point, and has a length about one-fourth as great as the width of the front of the head. Behind it the pharynx is somewhat prismoid and approximately one-fifth as wide as the head. It ends abruptly at the base. The pharynx is surrounded by a pharyngeal bulb, the musculature of which is set off distinctly from that of the oesophagus, in addition to which there is a constriction between the bulb and the oesophagus. The somewhat obscure, slender, apparently spiral amphids consist of about one and one-half winds. They are located opposite the posterior portion of the pharynx, and are one- FREE-LIVING FRESH-WATER NEMATODES 63 third as wide as the corresponding portion of the head. There are no eye- spots. The oesophagus begins as a tube three-fifths as wide as the base of the head, and it continues to have this diameter until it expands rather sud- denly to form a somewhat ellipsoidal or obscurely pyriform cardiac bulb, which is four-fifths as wide as the base of the neck, and contains an obscure, elongated, relatively narrow valvular apparatus. The lining of the oeso- phagus is a distinct feature throughout its length. There is no very dis- tinct cardia, but the preliminary cells of the intestine are different from those which immediately follow. The rather thick-walled intestine is separated from the oesophagus by a deep and distinct constriction, and becomes at once about half as wide as the body. Thereafter it widens out gradually so as to become three-fourths as wide as the body. It is composed of cells of such a size that probably about six to eight are required to build a circum- ference. The cells contain granules of variable size, the largest of which have a diameter half as great as that o'f the terminus of the tail. From the rather inconspicuous but slightly depressed anus the rectum, which is about as long as the anal body diameter, extends inward and forward. The body be- gins to taper slightly from some distance in front of the anus, but tapers more rapidly behind the anus in such fashion that at the beginning of the posterior fifth the diameter is about one-sixth as great as at the anus ; thence onward the tail is cylindroid, and ends in a tubular spinneret, less than half as wide as the terminus. The spinneret tapers slightly to a blunt point, and is armed at its base with one or more setae as long as itself. The caudal glands appear to be located in the base of the tail. The lateral fields are well-developed and fully one-third as wide as the body. The renette cell appears to be located a short distance behind the cardiac bulb. The position of the excretory pore is unknown, possibly it is at the base of the lips. The nerve-ring surrounds the oesophagus somewhat obliquely. From the elevated, rather broad vulva the vagina leads inward at right angles to the ventral surface fully half way across the body, where it joins the sym- metrically-placed uteri. The reflexed ovaries reach as far back as the vulva, at least in specimens in which the uteri contain no eggs. The fully de- veloped ova are nearly twice as long as the body is wide and about one- third as wide as long. The form, size and number of the eggs remains un- determined, but it seems probable that they occur in the uteri one at a time. Habitat: Spring, Washington Country Club, Ctu.y Chase, Md. Sublimate to balsam. MONHYSTERA, Bastian, 1865. Fig. 20, Plate VII. 62. .6 8.7 22. -72. 88. 17. Monhystera sentiens, n.sp. i.o mm. 1.0 3- 1 4-3 4-8 3-1 The thin, transparent layers of the colorless cuticle are traversed by about eight hundred transverse striae, resolvable with difficulty into rows of 64 NORTH AMERICAN somewhat dotlike elements. These striae are more readily visible toward the extremities, especially the posterior extremity. The conoid neck becomes convex-conoid toward the head, which is somewhat rounded. Throughout the body there are rather numerous, long, slender somatic setae having a length equal to the radius of the body. These setae are a little longer toward the extremities than they are near the middle of the body. On the outer margin of the head, a trifle in front of the base of the pharynx, there are ten spreading, tapering cephalic setae, one on each lateral line, and two of somewhat unequal size on each submedian line. The longest of these setae are more than half as long as the head is wide. A little more than twice as far back as the amphids there is a rather definite circlet of cervical or sub- cephalic setae arranged in submedian positions. The lips appear to be three in number, and are longitudinally striated or fluted. The thin flap-like, stri- ated portions are capable of assuming a revolute position. The basal por- tion of the lip region is considerably thicker than the flaps, and is arched over the margin of the pharynx. This latter is wide and shallow. Just beneath the lips it is two-thirds as wide as the front of the head. It closes together rapidly, so that its base is located at a distance from the anterior extremity about equal to the radius of the head. In other words, the pos- terior portion of the pharynx is about half way back to the amphids. These latter are circular, and one-third to one-fourth as wide as the correspond- ing portion of the head. Their distance from the anterior extremity is about equal to half the width of the front of the head. A short distance in front of each amphid there is a granular nucleus, which closely resembles the nerve cells that are found in the neck, and seems doubtless to be the nucleus of the nerve cell which is connected in some way with the function of the amphids. The oesophagus reaches to the base of the lips, and into it is set the posterior portion of the pharynx. At first the oesophagus is only two- thirds as wide as the base of the head. It continues to have this diameter, or a little more, until after it passes through the nerve-ring. Thence onward it gradually increases so that finally it is about two-thirds as wide as the base of the neck. The lining of the oesophagus is a fairly distinct feature. The intestine, which is separated from the oesophagus by a distinct constriction, is composed of cells of such a size that probably six to eight are required to build a circumference. The anterior portion of the intestine is somewhat bulbous in form, and is separated from the oesophagus on the one side and the true intestine on the other, by a pair of constrictions. This portion may be looked upon as a strongly developed cardia. The intestine is moderately thick walled, and ends posteriorly in a short, wide rectum, hardly as long as the anal body diameter. The posterior extremity of the female begins to taper from near the vulva, and continues to taper at about the same rate behind the tail as in front of it. The tail itself is conoid in the anterior four- fifths, and cylindroid in the posterior fifth. The terminus is hardly swollen, and is about one-sixth as wide as the base of the tail. The spinneret is rounded and bears a couple of submedian setae twice as long as its own FREE-LIVING FRESH-WATER NEMATODES 65 diameter. The three caudal glands are located in the anterior third of the tail. The lateral fields vary in width in different parts of the body. A little in front of the anus they are about two-fifths as wide as the corre- sponding portion of the body, and contain rather numerous scattered nuclei of such a size that about eight would be required to reach across the field. Farther forward the field is narrower, about one-fourth as wide as the middle of the body. Anteriorly it is wider, about one-third as wide as the base of the neck. Nothing is known concerning the renette. The nerve- ring surrounds the oesophagus somewhat obliquely a little in front of the middle of the neck. From the elevated and rather large and conspicuous vulva the vagina leads inward at right angles nearly half way across the body, where it joins the single uterus, which extends forward, and is of such a size as to contain apparently but one egg at a time. The ovary, which at first is three-fourths as wide as the body, extends forward and tapers gradually, so that at the blind end, considerably in front of the cardia and a short distance behind the nerve-ring, it is one-fourth as wide as the corre- sponding portion of the body. It sometimes happens that the blind end of the ovary is disposed in a single coil. The rather thick shelled eggs are as long as the body is wide, and about three-fourths as wide as long, and appear to be deposited before segmentation begins. The small spermatozoa found in the uterus are of such a size that at least ten placed side by side would be required to span the diameter of one of the eggs. There is a very small, posterior rudimentary branch to the uterus, which extends backward from the vulva a distance about equal to two-thirds the radius of the body. Around the vulva are four distinct, unicellular vaginal glands. 7i- .7 9.4 22. -M- 87. 1.5 mm. 1.6 2.9 3.5 4-2 3-3 The tail of the male resembles that of the female in form and size. As in the females, the three caudal glands are found in the anterior third of the tail, and do not extend materially farther forward than the anus. The two equal, L-shaped, slender, slightly tapering brownish spicula are a little longer than the anal body diameter. The anterior three-fifths lie nearly parallel to the body axis, while the posterior two-fifths are arranged nearly at right angles to the body axis. The distal extremities of the spicula are slightly widened. At their widest part, namely near the proximal ends, the spicula are about one-eighth as wide as the corresponding portion of the body. They are very slightly narrower distally than proximally, where they are barely cephalated by expansion. The accessory piece is not strongly developed. The main portion of it lies parallel to the distal two-fifths of the spicula, and is connected with the dorsal surface of the body by means of muscles. The ejaculatory duct is one-half as wide as the corresponding portion of the body. There are two outstretched testes. The blind end of the anterior testis is located a short ' distance behind the nerve-ring, while the blind end of the posterior testis is located about as far in front of the 66 NORTH AMERICAN anus as the terminus is behind it. The testes are broad and some parts appear to fill up the main portion of the body cavity. Habitat: Sand bar off Plummer's Island, Potomac River. Subli- mate to balsam. ONCHOLAIMELLUS, de Man, 1886. Fig. 21, Plate VII. 53 o 85 18 -M- QI 18. Oncholaimellus heterurus, n.sp. 1.2 mm. .8 1.5 1.8 1.8 1.4 The moderately thick layers of the transparent, naked, colorless cuticle seem to be destitute of markings of any kind. If there are any striations they must be exceedingly minute. The conoid neck becomes a little convex- conoid toward the head, which is subtruncated, and has a lip region almost imperceptibly expanded. There are ten long, curved, tapering, cephalic setae, located a trifle in front of the middle of the pharynx, two lateral, and eight submedian. The members of the submedian pairs are placed one in front of the other, the hinder members being only about two-thirds as long as the forward members. It is the forward members that are in the same circlet with the lateral setae. These latter are about as long as the longest submedian setae. The bases of the lips are nearly as thick as the wall of the head, but they gradually become quite thin, though the flaps are not so marked as they usually are in Oncholaimus. There are six lips, and each bears on its anterior surface, near the margin of the head, a somewhat out- ward pointing, minute, innervated papilla, which does not very markedly in- terfere with the contour of the front of the head. The somewhat cylindroid pharynx is about twice as long as the front of the head is wide, and the average diameter of the cavity is a little more than one-third of its length. At the middle the pharynx is about half as wide as the corresponding por- tion of the head. Its walls are fairly well chitinized, and appear to be des- titute of onchi. The description is derived from a single specimen, in which the mouth is filled with detritus, and it is possible that very minute teeth might have escaped observation, but this does not seem at all probable. The bottom of the pharynx where it is set on the end of the oesophagus, is in the shape of a broad, shallow, hollow cone. At a distance from the anterior extremity twice as great as the length of the pharynx the amphids are seen. These are somewhat elongated, roughly ovate in contour, and more distinctly marked anteriorly than posteriorly. The anterior border is a curved, chitinous structure about one-third as wide as the corresponding portion of the head. Slightly behind the anterior border the amphid has its greatest diameter. It is about as long as the corresponding radius of the head, and is extended backward by an apparently tubular structure, which soon becomes indefinite. Viewed dorso-ventrally the amphids appear like rather deep invaginations of the cuticle, and each occupies fully half of the FREE-LIVING FRESH-WATER NEMATODES 67 corresponding radius of the neck, and opposite them the oesophagus is a trifle narrower than it is either in front of or behind them. The oeso- phagus, which at first is about half as wide as the base of the head, con- tinues to have approximately the same diameter until after it passes through the nerve-ring, which is somewhat in front of the middle of the neck. Be- hind the nerve-ring the oesophagus becomes somewhat wider, and is finally about two-thirds as wide as the base of the neck. The lining of the oeso- phagus is a fairly distinct feature. The intestine, which becomes at once nearly three-fourths as wide as the body, is set off from the oesophagus by a distinct constriction. There does not appear to be any well developed car- dia. The cells composing the intestine contain scattered granules, which give rise to a very obscure tessellation, and also contain doubly refractive granules, which, however are not spherical in form, though their diameter in different directions is not very variable. The tail of the male tapers rap- idly from the anus, so that at the end of the anterior fourth it has a diameter but little greater than that of the terminal spinneret. Near the an- terior end of the cylindrical part there occur a pair of subventral arcuate, tapering setae, which are about as long as the corresponding diameter of the tail. In front of these there is a ventrally submedian pair of papillae, and also there is a dorsally submedian pair a little in front of these latter. The spinneret is of a simple character, and has the terminus almost imper- ceptibly swollen. There do not appear to be any setae on the spinneret. A trifle in front of the proximal ends of the spicula there springs from a ventrally submedian lines a somewhat weakly developed bursa, which extends slightly beyond the body contour, but only does this in front of the anus. It recedes into the cuticle at a point slightly in front of the caudal setae. This bursa does not have any ribs and is not striated in any way. The two equal, elongated, rather uniform, slightly cephalated spicula are a little more than twice as long as the anal body diameter, and in their anterior halves are nearly straight. In their posterior halves they are slightly arcuate. At the point where they attain their greatest width they are about one-fourth as wide as the corresponding portion of the body. Seen dorso- ventrally they are somewhat narrower and straighter than when seen in profile. The accessory piece appears to be compounded of a number of small chitinous elements, the whole structure being a little less than one- third as long as the spicula. It is not very strongly developed, and is not a very conspicuous feature. The ejaculatory duct is about half as wide as the corresponding portion of the body. There are two testes outstretched in opposite directions. The blind end of the anterior testis is about as far be- hind the base of the neck as this latter is behind the anterior extremity. The posterior testis is smaller, but just how much smaller is unknown, as its blind end could not be located in the single specimen examined. Little or nothing is known concerning the lateral fields and the renette. Habitat: Fresh water pond, near Ocala, Fla. Bouin solution to glycerine. 68 NORTH AMERICAN Note : There is some doubt as to whether this species should be as- signed to the genus Oncholaimellus for the following reasons: There are no pharyngeal teeth. The amphid varies somewhat from that of the type species. The spicula are of equal size, whereas in the type species orie of the spicula is only half as long as the other. CEPHALOBUS.. Bastian, 1865. Fig. 22, Plate VIII. 5i. 1 8 15 23 '61 04 19. Cephalobus sub-elongatus, n.sp. .6 mm. 1.6 3. 3-6 4-3 2.1 The thin, transparent, colorless layers of the naked cuticle are traversed by about seven hundred plain, transverse striae, resolvable with high powers without very much difficulty. The conoid neck becomes convex-conoid to- ward the obscurely lobed head, which is rounded in front, and is set off by an almost imperceptible, broad, exceedingly shallow constriction. There are no cephalic setae, and no eye-spots ; no amphids have been seen. There are three rather distinct, bluntly conoid lips, which are rounded in front, each of which apparently has two inconspicuous innervated papillae. The open vestibule leads to a conoid pharynx, which is about one and one-half times as long as the lip region is wide, and tapers from front to back in a com- paratively uniform way. Between the lips it has a width about one-third as great as that of the lip region. The posterior half of the pharynx rests in the anterior end of the oesophagus, which enlarges very perceptibly, so that a little behind the base of the pharynx it is more than half as wide as the corresponding portion of the head. It continues to have relatively much the same width until near the middle, where it is about three-fifths as wide as the middle of the neck. There it suddenly diminishes in size so as to be only one-fourth to one-fifth as wide as the corresponding portion of the neck. Passing through the nerve-ring with this narrow diameter it finally enlarges to form an ellipsoidal cardiac bulb about two-thirds as wide as the base of the neck, containing a rather distinct triplex but not very complex valvular apparatus of the form usually seen in this genus. There is no very definite cardia. The intestine, which is separated from the oesophagus by a rather broad and shallow constriction, is at first only half as wide as the corresponding portion of the body. It soon becomes thicker walled, and enlarges so as to be three-fourths as wide as the corresponding portion of the body. It is composed of cells of such a size that probably only about two are required to build a circumference. The contents of the cells are not distributed so as to give rise to anything distinct in the way of tessellation. The posterior lip of the anus is very slightly elevated. From the anus the rectum, which is somewhat longer than the anal body diameter, leads inward and forward. The rectum is separated from the intestine by a rather dis- tinct constriction. The tail is at first convex-conoid, the convexity existing FREE-LIVING FRESH-WATER NEMATODES 69 almost entirely on the dorsal surface. Through the middle third the tail tapers much more rapidly than elsewhere, so that at the beginning of the posterior fourth it has a diameter no more than one-fifth as great as at the anus. Thence onward it is conoid to the acute terminus. There is no spin- neret. Very little is known concerning the lateral fields, but at the middle of the body they appear to be one-third as wide as the corresponding portion of the body. There do not appear to be any distinct wings. The excretory pore is located opposite the nerve-ring. This latter surrounds the oesophagus obliquely, and is accompanied by nerve cells, of which the greater number are behind the nerve-ring and in front of the cardiac bulb. From the mas- sive elevated vulva the rather strongly chitinized, slightly colored vagina leads inward at right angles to the ventral surface nearly half way across the body, where it joins the single uterus, which extends forward. In speci- mens which do not yet contain fully developed eggs, and in which the uterus is occupied by spermatozoa, the flexure in the sexual apparatus occurs about half way between the vulva and the base of the neck. The ovary extends straight backward, and finally tapers to a blunt end a short distance in front of the anus. At the rear end the ovary is one-half as wide as the corre- sponding portion of the body. The ova appear to be arranged more or less single file in the greater part of the ovary, whose walls contain distinct nuclei of relatively large size. These nuclei are of such a size that about six to eight placed side by side would reach across the body, and are re- moved from each other in a longitudinal direction a distance equal to about two-thirds of the body diameter. None of these cells could be seen in that portion of the sexual tube in front of the vulva, and it is surmised that the cells composing the ovarian tube are markedly different in their character from those composing the tube between the ovary and the uterus and those composing the wall of the uterus. The spermatozoa have been seen packed in the uterus somewhat like a roll of coin, though each one is thinner at the margins than at the center where the nucleus exists. The spermatozoa are of such a size that the uterus may contain about two dozen, arranged single file. Habitat : Moss, Bog. W. End of Douglas Lake, Mich. This species close- ly resembles C. elongatus de Man, and possibly may prove to be the same. At present, judging from a single specimen it appears to differ in the following points: (i) The tail of the female is of different form, since that of elongatus is nearly conical ; (2) No wings have been seen on sub-elongatus, while they appear to be a marked feature of elongatus; (3) There is no expansion of the lip region in elongatus as in sub-elongatus; (4) The vulva in sub-elon- gatus is far more massive; (5) the pharynx in elongatus is more elongated, and longer as compared with the length of the head; (6) oesophagus is relatively slenderer in elongatus. Sublimate to balsam. 2.5 15. 31.6 Y 94. 20. Cephalobus setosus, n.sp. -7 mm- The moderately thick layers of the naked, transparent, colorless cuticle are traversed by 425 transverse striae, which are not further resolvable. 70 NORTH AMERICAN The striae are more or less interrupted on the lateral fields by two wings, or by a single wing indicated by two longitudinal lines. The width of the wing near the middle of the body is about equivalent to the width of four of the annules of the cuticle. Toward the tail end the width of the inter- rupted space is about equivalent to the width of three of the annules, and near the middle of the neck the width is also about equivalent to that of three of the corresponding annules. Through the middle of the lateral space on which the annules are interrupted there passes a longitudinal refractive line. The posterior portion of the neck is cylindroid; the anterior half conoid to the head, which is not set off in any way. The lips are arranged in two series: an outer series of six two-parted lips, and an inner series of three obscurely two-parted projecting flaps, each armed at the anterior rounded corners with short, arcuate, tapering, acute, forward-pointing bristles. Each of the two parts of the six outer lips or appendages is con- oid and acute, and the spaces separating them are much narrower than those separating the lips themselves. At the base of each of the lateral two-parted lips there is a transverse mark, which may possibly be the outer expression of the amphid. This marking is very minute and about four times as wide as it is long, and is placed transversely on the base of the lip, iust in front of the foremost cervical annule. It spans about one-sixth of the width of the head at this point. The three inner appendages, which may more properly be termed the lips, are about as long as they are wide, and seem to be flex- ible. They rather closely surround the mouth opening. Each is half as wide again at its free extremity as it is at the base, and the total length is about equal to one-fourth of the diameter of the front of the head. The setae with which these lips or flaps are armed are about two-thirds as long as the flaps themselves. The rather obscure, narrow, cylindroid pharynx is about as long as the base of the head is wide, and its lumen is hardly wider than the thickness of the cuticle. The oesophagus surrounds the pharynx, but is narrower in this region than it is immediately behind the pharynx. Behind the pharynx it commences as a tube about three-fifths as wide as the base of the head, and continues to have about the same diameter until after it passes through the nerve-ring. It does increase a trifle in diameter, however, so that at the nerve-ring it is about one-half as wide as the corresponding portion of the neck. Some distance behind the nerve-ring, namely, at a distance about equal to one and one-half diameters of the neck, there is a slight break in the musculature of the oesophagus. Behind this break the oesophagus begins to taper very gradually and continues to de- crease in diameter until it finally expands to form the somewhat ellipsoidal or pyriform cardiac bulb, which is about two-thirds as wide as the base of the neck, and contains a distinct, rather simple, triple, chitinized valvular appa- ratus. That portion of the oesophagus immediately in front of the cardiac bulb has a diameter about one-fourth as great as that of the corresponding portion of the neck. The lining of the oesophagus can be seen throughout its length, and is a fairly distinct feature. The intestine which at first is thin- FREE-LIVING FRESH-WATER NEMATODES /I walled is separated from the oesophagus by a distinct and deep constriction, and becomes at once about three-fourths as wide as the body. The anterior portion of the intestine is characterized by the presence of a considerable cav- ity, which, however, soon narrows, and, as the internal wall of the intestine is rather strongly refractive, the narrow, sinuous lumen is a very conspicuous feature. From the rather conspicuous depressed anus the rectum, which is rather strongly chitinized and somewhat longer than the anal body diameter, extends inward and forward. The tail is somewhat concave conoid from the anus to the very acute terminus. There are no caudal glands. The lat- eral fields appear to be about one-third as wide as the body. The nerve- ring surrounds the oesophagus somewhat squarely. The excretory pore appears to be located near the nerve-ring. The nature of the internal sexual organs remains uncertain, but the vulva is evidently located near the middle of the body. The description is derived from an immature specimen. Habitat: Cranberry bog, Arlington Farm, Virginia. Flemming so- lution to glycerine. BASTIANA, de Man, 1876. Fig. 23, Plate VIII. .2 8. 18. 58. 89. 21. Bastiana exihs, n.sp. - 1.4 mm. 5 -8 i. i. 5 i.i The moderately thick layers of the transparent, colorless, naked cuticle are traversed by about eight hundred forty transverse striae, which do not appear to be further resolvable. These striae exist in the outer as well as inner cuticle, so that the entire contour of the body is crenate. Rather con- spicuous lateral wings are present, the optical expression of which is two distinctly refractive longitudinal lines opposite the lateral fields, separated from each other by a distance somewhat greater than the width of one of the annules of the cuticle. The gradually tapering conoid neck ends in a somewhat truncate head, which is not set off in any way, and which bears a circlet of at least six cephalic setae, of which four submedian are the longer, and somewhat longer than the head is wide. Possibly each of these latter is accompanied by a shorter seta, thus making ten in all. Apparently labial papillae are present, but they have not been sufficiently clearly seen to permit of enumeration. There is no distinct pharynx. The amphids, lo- cated as in B. gracilis deMan, are somewhat in the form of the end of a shepherd's crook. They are perhaps to be regarded as broad spiral bands of about one turn. So regarded, the band may be conceived to begin on the ventral side where its end is rounded and its contour distinct, pass forward, and then curve backward and end indefinitely at a point somewhat in the rear of the beginning. The amphids are half to two-thirds as wide as the corresponding portion of the neck, and somewhat longer than wide. There are no eye-spots. The oesophagus begins as a tube fully two-thirds as wide as the head. It gradually increases in diameter as it passes backward, and at 72 NORTH AMERICAN its posterior extremity is three-fourths as wide as the base of the neck. There is no definite cardia. The lining of the oesophagus is indistinct. The intestine, which is separated from the oesophagus by an obscure constriction, becomes at once three-fourths as wide as the body, is rather thick walled, and its cells contain rather uniform, colorless granules, not arranged in any definite manner. From the rather raised anus the conspicuous rectum, which is twice as long as the anal body diameter, extends inward and forward. The tail is conoid, but tapers more rapidly near the acute terminus. A short distance in front of the terminus it is nearly half as wide as at the base. Nothing is known concerning the renette. The lateral fields have not been distinctly seen, but they appear to be about one-third as wide as the body. Nothing definite is known concerning the internal sexual organs, as the speci- mens examined were not fully developed. 60. .4 6. IQ. -M- 92. - 1.4 mm. .5 1.2 1.4 2. 1.2 The tail of the male is like that of the female in form and size, except that the anus is more prominently raised. In front of the anus and extending forward to the base of the neck there is a ventral row of ninety supplementary organs. These are of small size, and each ap- pears when seen in profile to be a slight conical, innervated elevation having an altitude about one-third as great as the width of its base. These organs are removed from each other a distance on an average about equal to the radius of the body or a little more. They are some- what nearer together posteriorly than anteriorly. Near the base of the neck the distance between two adjacent organs is about equal to the body diameter. The two equal, tapering, acute, nearly straight spicula are about one and one-third times as long as the anal body diameter. They are slightly cephalated by expansion, the cephalum occupying about one-third of the length. At the widest part, namely in the cephala, the spicula are one-fourth to one-third as wide as the corresponding portion of the body. They do not appear to have any accessory pieces. The spicula appear, when seen in profile, to be arranged at an angle of forty-five degrees to the body axis. Beginning at the anus and ex- tending obliquely backward there is a strand of muscle which is at- tached to the dorsal side of the body. The two testes are outstretched in opposite directions. The blind end of the anterior testis is about as far behind the base of the neck as the nerve-ring is in front of it, while the blind end of the posterior testis is about twice as far in front of the anus as this latter is in front of the terminus. Habitat: Fresh water, Tynne Station, Fla. Bouin solution to gly- cerine. FREE-LIVING FRESH-WATER NEMATODES 73 APHANOLAIMUS, de Man, 1880. Fig. 25, Plate VIII. 43- .5 8.8 20. '50.' 88. 22. Aphanolaimus spinferus, n.sp. - 1.5 mm .7 1.5 2.1 3.1 1.9 The thin, transparent layers of the colorless, naked cuticle are traversed by about one thousand transverse striae, which do not appear to be further resolvable, or at any rate are resolvable with difficulty. The cuticle is also traversed by longitudinal striations, manifestly due to subcuticular struc- tures, the submedian fields and the attachment of the muscle cells. The contour of the body is minutely crenate. There is .a distinct wing extending throughout the length of the body, whose presence is indicated by two re- fractive lines occupying a space hardly greater than the width of one of the annules of the cuticle. On being carefully examined these lines show traces of the striations of the cuticle. The conoid neck ends in a somewhat rounded head, whose lip region is set off by a minute constriction just in front of the amphids. The contour of the front of the head is rounded, or, like that of a very flat truncated cone. In the midst of the truncation there is an exceedingly minute depression, the mouth pore. There does not appear to be any very distinct pharynx, but the lining of the oesophagus is slightly altered in the region of the head back as far as the posterior margins of the amphids. It is not unlikely that this represents a distinct, though rudi- mentary pharynx. The species, however, would naturally at first sight be classed as being without a pharynx. The oesophagus begins as a tube about half as wide as the base of the head, and expands very gradually until after it passes through the nerve-ring. At the nerve-ring its width is about one- third that of the corresponding portion of the neck. Behind the nerve-ring the oesophagus begins to expand a little more rapidly, though still slowly. When it reaches the end of the neck it is half as wide as the base of the neck. For a distance equal to one body diameter, however, it decreases in size, so that where it joins the intestine it is very narrow, only about one- fifth as wide as the corresponding body diameter. Nevertheless, there ap- pears to be a distinct, though exceedingly minute cardia. The lining of the oesophagus is a fairly distinct feature throughout its length. The intestine, which is at first thin-walled, gradually becomes half as wide as the body, and is composed of cells of such a size that only two or three are required to build a circumference. For the most part the wall of the intestine is moder- ately thick. From the very slightly raised, rather inconspicuous anus the slender rectum, which is about one and one-half times as long as the anal body diameter, extends inward and forward. It is separated from the in- testine by a very distinct and deep constriction. Near the middle the lateral fields are about one-third as wide as the body. The ventral gland is a rather elongated, saccate cell a little longer than the base of the neck is wide, and about one-third as wide as long. It contains a large spherical nucleus, 74 NORTH AMERICAN with a large, fairly distinct nucleolus. There extend backward from this cell two finger-shaped, submedian extensions nearly as long as the cell itself. Notwithstanding the distinctness of the organ and appendages the position of the excretory pore remains to be discovered. The tail tapers from in front of the anus in such fashion that at the beginning of the final fourth it has a diameter about one-fourth as great as at the anus. Thence onward the tail is cylindroid to the terminus, which bears a trun- cated, conical, unarmed spinneret. The three caudal glands are minute, close together, opposite to and a little behind the anus. From the slightly depressed vulva the chitinized vagina leads inward at right angles to the ventral surface half way across the body, where it joins the two symmetrical- ly placed uteri. The reflexed ovaries reach about one-third the distance back to the vulva and contain a few developing ova arranged single file. The species is viviparous. Two embryos and a developing egg have been seen in each uterus at the same time. The eggs are somewhat elongated, about as long as the body is wide, and a little less than half as wide as they are long. 64 .2 10. I4.(?) M 82. 1.5 mm. .7 i.i 2. 2.4 1.9 The tail of the male is like that of the female in form and size. In front of the anus there is a ventral series of seven tubular, protrudable, sup- plementary organs, occupying a space nearly equal to the length of the tail. The hindermost is opposite the proximal ends of the spicula. Each of these organs is about half as long as the body is wide, has its proximal end slightly cephalated by expansion, and its distal end slightly curved. The circular apertures through which the organs are protruded disturb the ventral con- tour distinctly, each of them occupying a space about equal to the width of four annules of the cuticle. There are no special setae or papillae either in front of the anus or behind it. The two equal, uniform, slender, very strongly arcuate spicula are about one and one-half times as long as the anal body diameter, and their proximal ends are cephalated by expansion. The proximal ends lie nearly opposite the body axis. There is a simple ac- cessory piece, applied for a short distance to the distal ends of the spicula, having a backward pointing process two-thirds as long as the anal body diameter. Habitat: Potomac River, Washington, D. C. Sublimate to balsam. 3i 23. Aphanolaimus minor, n.sp. * .6 mm. 8 3-3 3-9 4-7 2.6 The moderately thin, transparent layers of the colorless, naked cuticle are traversed by fine transverse striae, resolvable with moderate powers, and not modified on the lateral fields. The presence of wings is indicated by two lines extending from near the middle of the neck well onto the tail. FREE-LIVING FRESH- WATER NEMATODES 75 These occupy a space a little more than the width of one of the annules of the cuticle, but sometimes one of these lines is more prominent than the other. The conoid neck ends in a rounded head, which is not set off in any way. There are no cephalic setae. There does not appear to be any distinct pharynx. The lining of the oesophagus is slightly modified back twice as far as the posterior margins of the amphids, and very likely this portion of the tube may be regarded as a narrow rudimentary pharynx. Twice as far from the anterior extremity as the base .of this supposed pharynx the oesophagus is distinctly interrupted by a break in the musculature, although there is no change in size, and just behind this break there are three distinct, elongated nuclei, one in each segment of the oesophagus. These appear- ances are reminiscent of the arrangement in Plectus, to which Aphanolaimus is doubtless related. There do not appear to be any distinct lips, though possibly there may be three exceedingly minute, well amalgamated, flattish ones. Although at first glance the amphids appear to be circular, they are really spiral in form. They are about one-fifth as wide as the corresponding portion of the neck. Their distance from the anterior extremity is about equal to the diameter of the head; or in other words, their centers are re- moved from the anterior extremity a distance about twice as great as their diameter. The amphids appear to be slightly larger in the male than in the female. There are no eye-spots. The oesophagus begins at the base of the above described pharynx, as a tube about half as wide as the corresponding portion of the neck. It widens very gradually, so that where it passes through the nerve-ring it is nearly one-third as wide as the corresponding portion of the neck. At the middle, nearly opposite the nerve-ring, there is an almost imperceptible increase in diameter, indicative of a deteriorated median swelling. Finally, it expands into the narrowly pyriform cardiac swelling destitute of any distinct valvular apparatus. This swelling is half to two-thirds as wide as the base of the neck. The lining of the oesophagus is a distinct feature throughout its length. There is no distinct cardia. The intestine, which is at first only one-fifth as wide as the base of the neck, joins the middle of the posterior surface of the cardiac swelling. It is moderately thick-walled, and gradually becomes about two-thirds as wide as the body. It appears to be made up of cells of such a size that few, prob- ably two or three, or possibly four, are required to build a circumference. The body tapers gradually from a long distance in front of the anus. This latter is very slightly raised, more particularly on the anterior margin. From it the rectum, which is about as long as the anal body diameter, extends in- ward and forward. The tail is conoid in the anterior three-fourths. The posterior fourth is cylindrical and has a diameter nearly one-third as great as that of the base of the tail. It ends in a rounded, unarmed spinneret, bear- ing an apiculum. The lateral fields appear to be about one-third as wide as the body. The nerve-ring surrounds the oesophagus somewhat obliquely. There appears to be a small renette cell opposite the anterior portion of tire intestine, but the position of the excretory pore has not been discovered. 76 NORTH AMERICAN From the inconspicuous vulva the vagina leads inward at right angles to the ventral surface about half way across the body, where it joins the two sym- metrically-placed uteri. The reflexed ovaries reach about half way back to the vulva and contain half a dozen or more developing ova arranged somewhat irregularly. The thin-shelled, ellipsoidal eggs are about as long as the body is wide and about three-fifths as wide as long. They have been seen in the uterus one at a time, and apparently are deposited before seg- mentation begins. 3. 15. 23. -M- 85. .5 mm. 1.8 3.4 3.8 4-2 34 The tail of the male is conoid in the anterior three-fourths in such fashion that the beginning of the final fourth has a diameter of about one- eighth that of the base of the tail ; thence onward the tail is nearly cylin- drical or expands slightly, and ends in a rounded terminus bearing an api- culum forming an unarmed spinneret. The caudal glands are located in the base of the tail. In front of the anus in the male there is a ventral row of eight or nine protrudable. obscurely S-shaped, yellowish supplementary or- gans. These appear to be of rather uniform size and are equally spaced. Their length is somewhat greater than that of the radius of the body, and they are placed at an angle of about thirty degrees to the body axis. They are of rather uniform diameter throughout their length, but taper a little toward the blunt distal extremity, and are obscurely cephalated at the proximal ends. The distal extremity of the hindermost of these organs is located nearly opposite the proximal ends of the spicula. The entire distance occupied by the series is about one and one-half times as great as the length of the tail. The two equal, tapering, strongly arcuate, brownish yellow spicula are about one and one-half times as long as the anal body diameter. Their proximal ends are cephalated by expansion, and extending from the proximal ends toward the distal extremities there are straight, refractive lines indicat- ing possibly that there is more to the framework of the spicula than appears at first glance. The spicula curve inward and backward to near the dorsal side of the tail, and then pass forward so that their proximal extremities lie opposite the body axis. The spicula are accompanied by a rather straight, slender, slightly tapering, blunt accessory piece applied to their distal fifths. From this point the accessory piece extends inward and backward at an angle of sixty degrees, and ends a little to the dorsal side of the body axis. At their widest part, just behind the cephala, the spicula have a width about one-fifth as great as that of the corresponding portion of the body. A little behind the middle of the tail there are two ventrally sub- median setae, about half as long as the corresponding diameter of the tail. The ejaculatory duct is about one-third as wide as the body. There are two testicles, one extending forward and the other backward. The blind end of the anterior testicle is a little farther behind the base of the neck than the FREE-LIVING FRESH-WATER NEMATODES 77 nerve-ring is in front of it. The blind end of the posterior testicle lies just in front of the anterior supplementary organ. Habitat: Mud, Potomac River. Sublimate to balsam. TYLENCHUS, Bastian, 1865. 60 24. Tylenchus symmetries, n.sp. 2 -7 108 17. -49- 90.2 mm i-4 2.8 3.3 3.8 2.7 The moderately thick layers of the transparent, colorless, naked cuticle are traversed by fine plain transverse striae, which are not further resolvable. There are two wings on the lateral fields, removed from each other a dis- tance about equal to one-fourth to one-fifth the body diameter. The space between these wings is very faintly marked with longitudinal lines, of which two near the middle are more prominent than the others. The wings them- selves bear traces of transverse striation. These wings begin near the middle of the neck and end on the tail. The conoid neck becomes convex- conoid toward the somewhat rounded head, which is not set off, or at least only by an almost imperceptible constriction a short distance behind the lip region. There are no distinct lips. What appear to be the faintest possible traces of papillae may be seen on the lips, but these do not disturb the rounded contour of the head. Were it not for the innervations it would be prac- tically impossible to see them. The pharynx is tubular and just wide enough to make a passage for the spear. This latter is slender, nearly one and one- half times as long as the base of the head, and has a three-bulbed base about one-fifth to one-fourth as wide as the corresponding portion of the head. Near the middle the spear is closely surrounded by a rather inconspicuous guiding-ring or cylinder, about one-fourth as long as the spear. At its widest part, namely, in the proximal half, the diameter of the spear is less than the width of two of the adjacent annules of the cuticle. The oesophagus begins as a tube about one-third as wide as the base of the head, and con- tinues to have this diameter until it expands to form the ellipsoidal or pro- late median bulb. This latter is about three-fifths to two-thirds as wide as the middle of the neck, and contains a distinct ellipsoidal valvular apparatus about one-fifth as wide as the bulb itself. Behind the median bulb the oesophagus is smaller than elsewhere. For a distance equal to twice the width of the neck it has a width only about one-eighth to one-sixth as great as that of the corresponding portion of the neck. There- after, it expands to form the elongated-pyriform non-muscular cardiac swell- ing, which is half as wide as the base of the neck, and contains a rather conspicuous nucleus. The lining of the oesophagus is a fairly distinct feature in its anterior part; but posteriorly it is much less distinct, and is very diffi- cult to observe in the cardiac swelling. The intestine, which is separated from the oesophagus by an indistinct constriction, becomes at once fully two- thirds as wide as the body. Its cells are packed with large granules of some- what variable size, the largest of which have a diameter about one-eighth as great as that of the body, the smallest being considerably smaller. These 78 NORTH AMERICAN granules are so prominent as to obscure the cellular structure of the in- testine. From the very slightly elevated and rather inconspicuous anus the rectum, which is hardly as long as the anal body diameter, extends inward and forward. The tail is conoid to the terminus, where it rather suddenly tapers much more rapidly to a very acute point. This rapidly tapering por- tion has a length about equal to one-fourth the anal body diameter, and the diameter at the point where the change in taper begins is about equal to one- fifth of the anal body diameter. The lateral fields appear to be a little more than one-third as wide as the body. The nerve-ring surrounds the oesopha- gus obliquely. The excretory pore is located a little behind the nerve-ring, a little more than half way from the base of the neck to the middle of the median bulb. From the slightly elevated, rather massive vulva the vagina leads inward at right angles to the ventral surface nearly half way across the body, where it joins the two uteri. Apparently the ovaries are out- stretched. A single egg has been seen in one of the uteri. It is about twice as long as the body is wide and about one-third as wide as long. It is thin- shelled and apparently undergoes segmentation before being deposited. 3.1 13.5 20.5 -M 3 89.1 2.2 3.6 3.9 4.2 3.2 The tail of the male is like that of the female in form. From the raised anus it is arcuate-conoid to the terminus, which is concave-conoid and ends in an exceedingly fine slender point. The length of the terminus is about one-third as great as the anal body diameter, while its diameter is about one-fourth as great as the anal body diameter. There are no supplementary organs, nor have any special papillae been seen either in front of the anus or behind it. There is a fairly well developed, but not very prominent bursa, which extends but little beyond the ventral contour at any point. It springs from the submedian lines at a distance as far in front of the anus as the middle of the tail is behind it. The bursa is striated like the cuticle, and its margin is entire; it extends to near the end of the tail. Near the middle of the tail there appears to be a bursal rib on each side, which does not reach to the margin of the bursa. The ejaculatory duct is about one-third as wide as the body. The blind end of the single outstretched testicle lies a short distance behind the base of the neck. Habitat : Marsh in black clay with much decayed vegetation, near Im- patiens, Arlington Farm, Virginia. Flemming solution to glycerine. RHABDITIS, Dujardin, 1845. 7i 1.2 10.8 16.8 '55' 93.8 25. Rhabditis punctata, n.sp. - 1.8 mm. 1.2 3.3 4.3 4.9 1.6 The thin layers of the transparent, naked, colorless cuticle are traversed by transverse striae, which are resolvable with high powers and appear to be resolvable into rows of dots, but there is some doubt about this. The cuticle FREE-LIVING FRESH-WATER NEMATODES 79 is longitudinally striated. Near the middle of the male there is a lateral area nearly half as wide as the body, which is nearly destitute of striations. On either side of this field the cuticle may be seen with high powers to be dis- tinctly longitudinally striated. This lateral field narrows toward both ex- tremities so as to be hardly wider than the spicula, so that the main portion of the cuticle of these regions appears there to be longitudinally striated. The neck is conoid, becoming almost imperceptibly convex-conoid toward the head, which is somewhat rounded and bears six lips, which are fairly well separated from each other, and each of which appears to be papillate. The simple, unarmed pharynx is cylindrical and one-third as wide as the base of the head. Its cavity is four to five times as long as wide. No amphids have been seen, and there are no eye-spots. The oesophagus receives the base of the pharynx and becomes at once about two-thirds as wide as the base of the head. It continues to have this diameter until it expands to form the ellipsoidal median swelling, which has a distinctly radiated fibrous structure. This swelling is about two-thirds as wide as the corresponding portion of the neck, and is separated from the portion of the oesophagus preceding it, as well as the portion succeeding it, by a refractive division in the internal musculature. Behind the median swelling the oesophagus has a diameter less than half as great as that of the corresponding portion of the neck, and it narrows continuously until it reaches the pyriform cardiac bulb, which is three-fourths as wide as the base of the neck and contains a well developed, complicated, chitinous valvular apparatus half as wide as the bulb itself. There is no distinct cardia. The somewhat transparent and colorless intestine, which is separated from the oesophagus by a distinct constriction, is composed of cells containing scattered granules of variable size, the largest of which have a diameter somewhat less than the thickness of the cuticle, and the smallest of which are very much smaller. The anus is slightly raised, and from it the rectum, which is one and one-half times as long as the anal body diameter, leads almost directly forward. The body tapers for some distance in front of the anus; from the anus onward it is conical to the acute terminus. There is no spinneret, and there are no caudal glands. Nothing definite is known concerning the renette cell. The excre- tory pore is located about half way between the median and posterior bulbs, just behind the oblique nerve-ring. The two uteri extend in opposite direc- tions, and the ovaries are reflexed, the flexures occurring the one not far behind the base of the neck and the other not far in front of the anus. The mature females contain scores of eggs in various stages of development, the most advanced containing well-developed embryos. 63 2.3 16.2 25.9 -M 96.3 i. mm. i-9 34 3-5 3-7 2.6 The tail of the male is conoid from the anus in such fashion that at the beginning of the posterior third it has become reduced to a mere striated nearly straight spine, which is no wider than one of the ribs of the bursa. 8O NORTH AMERICAN The dorsal contour of the tail continues as a more or less regular extension of that of the body. The ventral contour, however, is elevated at the anus; at any rate, when the spicula are partly extruded. This elevation appears to be largely median, and there is a distinct groove on either side between it and the bursa. When this groove is brought into optical section and the anal elevation is disregarded the tail appears to be asymmetrically conoid. The two equal, brownish, nearly straight spicula are fully twice as long as the tail, or one and one-half times as long as the body diameter, measured oppo- site the proximal ends of the spicula. The spicula in the distal three-fourths taper to a blunt point. At their widest part, considerably in front of the middle, they are one-fourth to one-fifth as wide as the corresponding portion of the body. In the proximal fourths the spicula are rather suddenly nar- rowed and terminate in bulbs or cephala, which have a diameter twice as great as the portion of which they are expansions. Parallel to the spicula there are accessory pieces. These are two-thirds to three-fourths as long as the spicula, which they partially envelop. They are about as strongly chitin- ized as the spicula themselves. The transparent, colorless bursa springs from the submedian lines, nearly opposite the proximal ends of the spicula, and when seen in profile only slightly exceeds the ventral contour in front of the anus, but behind the anus exceeds the ventral contour of the tail proper so much that nearly the entire length of the ribs comes plainly into view. The ribs are arranged in three groups: (i) Two ribs close together opposite the middle of the spicula. (2) Four ribs close together opposite to, and a trifle behind the anus. (3) Four ribs of which three are very close together, and one a little farther forward, the whole group being opposite the middle of the tail. Most of these ribs reach to the margin of the bursa, which is entire and is not distinctly striated. The outer members of the middle and posterior groups do not reach quite to the margin. The ejacu- latory duct is nearly one-half as wide as the body. The single, outstretched testicle has its blind end located about half as far behind the base of the neck as this latter is behind the anterior extremity. At its blind end the testicle is about one-third as wide as the body. It gradually increases in width, so that it occupies four-fifths of the diameter of the middle of the body. The spermatocytes are of large size, one-third to one-half as wide as the body. Habitat : About the roots of aquatic plants, Potomac River, Washing- ton, D. C. TRILOBUS, Bastian, 1865. Fig. 15, Plate VI. 40 26. Trilobus longus, (Leidv), Bastian^ * 9 ' 46 ' ^ 1.2 mm. 2. 2.8 3.8 4.6 2.3 The thin, transparent layers of the colorless cuticle are traversed by exceedingly fine plain transverse striae, more particularly visible in the FREE-LIVING FRESH-WATER NEMATODES 8l lower layers with high powers. There are short hairs to be found here and there on the surface of the body, more particularly toward the ex- tremities. The conoid neck ends in a somewhat rounded head not set off by any constriction. The cephalic setae appear to be ten in number (eight submedian and two lateral), outward pointing, each about one- sixth as long as the head is wide, and placed on the outer margin of the front of the head opposite the posterior portion of the pharynx. The members of the submedian pairs are, however, of unequal size. There are six small, pointed lips surrounding the mouth opening. It is cer- tain that these lips bear papillae, but the number is not known. Lat- eral organs in the form of somewhat stirrup shaped markings one- fourth as broad as the corresponding portion of the head, occur at a short distance behind the base of the rudimentary pharyngeal cavity. This latter is a more or less triquetrous cyathiform cavity having its walls distinctly chitinized and bearing at its base one or more protuber- ances near the point where the lumen of the oesophagus begins. One of these is a ridge, the others minute teeth. The average width of the main pharyngeal cavity is about one-third that of the head. The oeso- phagus is slightly expanded to receive the pharynx, but otherwise be- gins as a tube about three-fifths as wide as the anterior part of the neck, and expands very gradually to the end, where it is a little more than half as wide as the base of the neck. The lining of the oeso- phagus is a distinct feature throughout its length. There is a distinct rounded cardia. The intestine, which becomes at once about two-fifths as wide as the body, is separated from the oesophagus by a distinct constriction, in which lie the three granular bodies whose presence gave origin to the name of the genus. The intestine is relatively thick walled, its small cells containing scattered granules of small size, which are not arranged in any very definite manner. The intestine frequently contains diatoms in large numbers, thus indicating that these are a common source of nourishment for this species. From the slightly de- pressed anus the rectum, which is about as long as the anal body diameter, extends inward and forward to join the intestine, which is narrowed at its extremity so as to be about two-fifths as wide as the body. Nothing is known concerning the ventral gland. The longi- tudinal fields are distinctly developed, being about one-fourth as wide as the worm itself. The nerve-ring surrounds the oesophagus some- what obliquely. The tail is conoid in the anterior third in such fashion that at the beginning of the middle third it has a diameter about one- fourth as great as at the anus. Thence onward it tapers gradually to the slightly swollen spinneret or outlet for the caudal glands. These latter, three in number, are located tandem in the tail opposite to and slightly behind the anus. From the slightly elevated vulva the vagina leads inward at right angles to the ventral surface fully half way across the body. The vagina is bifurcated and extends in opposite di- 82 NORTH AMERICAN rections, the reflexed ovaries passing about two-thirds the way back to the vulva. Two or three eggs may occur in each uterus at one time. These are somewhat ellipsoidal and thin shelled, being about two-thirds as long as the body is wide and about two-thirds as wide as long. The eggs appear to indicate at least the early stages of segmentation before being deposited. The walls of the vagina present the peculiarity of being very thick, and composed of concentric layers to the number of six or seven, so that the organ is considerably broader than it is deep. Its in- ternal wall presents the peculiarity of staining strongly with carmine. 1.3 8.3 137 -M- 92. ^ ^ 2. 2.6 3.2 3.8 2.7 The tail of the male is very much like that of the female in form and size. Supplementary organs are found in front of the anus only. These are six in number, of which three are very prominent. The an- terior member of this group of three is about twice as far in front of the anus as the spinneret is behind it. The members of this group are equidistant, the distance between consecutive members being about twice as great as the diameter of the organs themselves. All three occupy a distance about twice as great as the corresponding body diameter. Each of these organs consists of an internal and an external portion, the internal portion being a flattish, hemispherical mass of tissue of very fine, or at least uniform texture. These have a diameter about two- fifths as great as that of the body at the same part. The external portion of these organs consists of a ring slightly raised, from which projects a mammiform papilla which bears a minute median seta or nerve-ending. When this mammiform portion is traced inward it passes through the ring on the surface of the body and then bends forward and ends rather indefinitely in the anterior contour of the internal por- tion of the organ. These organs possess the peculiarity of staining strongly with carmine. In addition to the organs already described there are three others of smaller size, two very minute, one near the anus and the other opposite the proximal portions of the spicula. The third, which has a size intermediate between those just described and those first described, is located about half way between the anus and the posterior member of the larger group. These smaller organs are comparatively close counterparts of the larger, differing merely in size. In addition it may be noted that the cuticle on the ventral surface of the male throughout this region of the body, that is, as far forward as the most anterior of these organs, bears about twenty exceedingly minute structures on the ventral line, which appear to be innervated papillae. These also stain strongly with carmine, although they are so minute as to be difficult to observe. There are no papillae on the tail, but there are several short hairs, more particularly near the ventrally submedian lines. There is no bursa. The ejaculatory duct is coexten- sive with the supplementary organs. It is on the average nearly half FREE-LIVING FRESH-WATER NEMATODES 83 as wide as the corresponding portion of the body. It is connected with the seminal vesicle by a narrow portion. The seminal vesicle is elon- gated, about half as wide as the body, and extends to a point about as far behind the neck as the base of the neck is from the anterior ex- tremity. From this point the two nearly equal testicles extend in oppo- site directions, and end blind, one not far behind the base of the neck, and the other not far from the middle of the body. These possess the peculiarity of being slightly swollen at their proximal ends just where they join the vesicle. These swellings appear to constitute veritable cavities of small size. That region of the body corresponding to the ejaculatory duct is traversed by oblique striae, which, however, are ar- ranged at right angles to the direction of such oblique striations as are found in other genera, and it is probable that they are connected with the duct itself, and are not muscles of the character which usually give rise to these oblique striations on the males of other genera. The two equal, arcuate slender spicula appear to be of rather uniform diameter when viewed laterally, and are one and one-half times as long as the anal body-diameter. Their proximal ends are cephalated by contrac- tion. They are accompanied by accessory pieces two-fifths as long as the spicula themselves, and arranged parallel to the distal portions of the spicula. Habitat: Mud, about the bases of aquatic plants, Potomac river, D. C. MESOMERMIS, Dady. Fig. 18, Plate VII. Fig. 24, Plate VIII. 55 - ,, .8 6.3 ii. -M- 96. 27. Mesomermis virgimana, n.sp. 1.8 mm. 1.3 2. 1.8 2.3 2.2 The rather thick, transparent, colorless layers of the naked cuticle are destitute of transverse striations. There are minute longitudinal striations throughout the body. These are interrupted on the lateral lines, where there is a distinct wing. The conoid neck becomes convex- conoid toward the lip region, which is not set off in any way. There are no cephalic setae, and there is no distinct pharynx. The mouth pore is very minute, and is a little toward the ventral side of the middle of the front of the head. The cuticle has about the same thickness on the head as elsewhere, being only a trifle thicker. The cuticle is pene- trated on the head by a number of innervations. These end in minute depressions on the surface of the head. Near the mouth opening there is one of these depressions on the dorsal side, and apparently a sim- ilar one on the ventral side, while nearer the outer margin of the head there are two ventrally submedian and two dorsally submedian similar depressions. Pores occur also here and there on the body as well as on the neck. There are no eye-spots. The lateral organs present the 84 NORTH AMERICAN following appearance when seen from the side : They appear to project from the surface of the body very slightly, beginning as a tube having a length about one-third as great as the corresponding diameter of the head. This tube has very thin walls, and a short distance in, appar- ently near the surface of the body, a second element appears in the form of a circle inside that representing the contour of the outer tube. This appears to constitute a sort of core in the midst of which are a number of refractive elements, resembling nerve fibers, which pass in- ward and backward toward the lumen of the oesophagus. Some of these elements are longer than others. The focus passing inward picks up one, then two, then several more, so that by the time a view is ob- tained that is wholly inside the body there are seen a half dozen or more of these elements. It is impossible in this view to pick up an in- ternal connection of these refractive elements. The oesophagus begins just below the transparent cuticle as a very narrow tube, probably not more than one-eighth as wide as the corresponding portion of the neck. It continues to have this diameter until after it passes through the nerve- ring. At a distance from the nerve-ring equal to about one body diam- eter, the oesophagus begins to change gradually into intestine. The intestine gradually widens out, so that at a point as far behind the nerve- ring as the neck is wide it has a width one-third as great as that of the body. It goes on increasing in this way until at a distance from the nerve ring three times as great it is two-fifths as wide as the body. Near its middle the intestine is half as wide as the body. The cells of the intestine contain granules of variable size, the largest having a diameter fully twice as great as the thickness of the cuticle, and the smallest being very minute. The female has not been seen. The tail of the male is slightly arcuate, and is conoid to the blunt, rounded terminus, which has a diameter half as great as that of the base of the tail. There is no spinneret, and there are no caudal glands. The lateral fields are about one-third as wide as the body. The nerve- ring surrounds the oesophagus somewhat obliquely. Nothing is known concerning the ventral glands or the excretory pore. The tail of the male bears several series of innervated papillae. These are sufficiently elevated at the surface of the cuticle to slightly break the contour when the tail is seen in exact profile. Where each nerve passes through the cuticle there is a very low, almost imperceptible elevation at the sur- face. These papillae are arranged on the ventral submedian lines as well as on the ventral line. The ventral papillae just in front of and just behind the anus are double. As to particulars of the submedian group, there are four on the tail, one member opposite the anus; one a little farther back, a third near the middle of the tail, and a fourth considerably farther back. In front of the anus on each side are eight submedian papillae. These occupy a distance more than twice as great as the length of the tail, and the distance between successive papillae in- FREE-LIVING FRESH-WATER NEMATODES 85 creases with the distance from the anus, so that the space between the seventh and eighth is about two-thirds as great as the diameter of the body. Of the median papillae on the tail there are three; two near the anus, and one just in front of the middle of the tail, with pos- sibly a fourth farther back. In front of the anus, of the median papillae there are two near the anus, and ten additional ones about coextensive with the submedian rows and distributed in the same manner, the dis- tance between successive papillae increasing with the distance from the anus. The two equal, arcuate, uniform, blunt spicula are about one and one-third times as long as the anal body-diameter. Their proximal ends are not cephalated. The ejaculatory duct is about one-third as wide as the body. The vas deferens is about one-half as wide as the body. There are two outstretched testicles, the blind end of the anterior being about twice as far from the end of the neck as this latter is from the anterior extremity. The posterior testicle is a little shorter than the anterior. Habitat: Cranberry bog, Arlington Farm. ACHROMADORA, Cobb, 1914. Fig. 11, Plate V. 28. Achromadora minima, Cobb. For original description see Macleay Memorial Volume, Sydney, 1893; see also Journal Washington Academy of Sciences, Oct. 4, 1914. 86 NORTH AMERICAN EXPLANATION OF PLATES* PLATE II. IOTA, Cobb, 1913. Fig i. Iota octangulare, n. sp. Lateral view of a female specimen. a, lip region; b, labial chitinous plate or expansion; c, protruding muscles of the spear ; d, spear ; e, trilobed base of the spear ; f, lumen of the oesophagus ; g, nerve-ring; h, beginning of the intestine; i, flexure in the single narrow ovary; j, excretory pore; k, ventral row of modified cuticular elements; /, submedian row of modified cuticular elements; m, ovum; n, muscular layer; o, anterior extremity of the uterus ; p, uterus ; q, cuticle ; r, vulva ; s, sub- median row of modified cuticular elements ; t, rectum ; u, anus ; v, terminus. RHABDOLAIMUS, de Man, 1880. Fig. 2. Rhabdolaimus minor, n. sp. I, lateral view of female; II, head of the same, showing amphid. The head in I is twisted, so that the amphid appears as if ventral, or nearly so. a, amphid ; b, long, narrow pharynx ; c, anterior group of nerve cells ; d, nerve-ring ; e, cardiac bulb ; /, wall of the intestine ; g, flexure in anterior ovary; h, posterior group of nerve cells; i, body cavity; j, lumen of intestine; k, ovum; I, blind end of posterior ovary; m, egg; n, flexure in posterior ovary ; o, cuticle ; p, caudal glands ; q, subcuticle ; r, vulva ; s, rectum ; t, anus ; u, nerve cells (?) ; v, duct of caudal glands; w, spinneret; x, lip region. DIPLOGASTER, Max Schultz, 1857. Fig. 3. Diplogaster fictor, Bastian. I, side view of female; II, head of the same seen in dorso-ventral view, lips nearly closed ; III, head of the same, lateral view, lips nearly wide open; IV, head of the same, lateral view, lips partially closed; V, front view of mouth, partially closed; VI, lateral view, posterior portion of a male specimen; VII, somewhat dia- grammatic perspective view showing markings of the cuticle. a, one of the lips ; b, one of the six cephalic setae ; c, amphid ; d, one of the two more or less evertible pharyngeal hook-shaped teeth; e, median oesophageal bulb ; /, nerve-ring ; g, anus ; h, rectum ; i, intestine ; j, terminus ; k, posterior oesophageal bulb; /, nerve cells; m, renette cell (?); n, left spiculum; o, lumen of the intestine; p', preanal male seta; p" , P' ' ' , p' ' ' ' , post-anal male setae and papillae; q, one of the cells of the intestine; r, accessory piece ; s, flexure in anterior ovary ; t, blind end of anterior ovary ; u, longitudinal striae of the cuticle ; v, vagina ; w, synapsis in egg in the an- terior uterus, the reduced number of chromosomes being seven; x, one of the spermatozoa in the ovary; y, uterus; z, vulva. *The drawings are used by permission of the Secretary of Agriculture, and were made by Mr. W. E. Chambers, under the author's supervision. FREE-LIVING FRESH-WATER NEMATODES 9 Fig. 2. Rhabdolaimus minor, n. sp Fig. 3. Diplogaster fictor, Bastian. PLATE II. 88 NORTH AMERICAN PLATE III. PRISMATOLAIMUS, de Man, 1880. Fig. 4. Prismatolaimus stenurus, n. sp. I, lateral view of a female; II, front view of head ; III, side view of head. a, one of the six cephalic papillae ; b, one of the ten cephalic setae ; c, one of the six thin lips; d, pharynx; e, amphid; f, lumen of the oesophagus; g, nerve-ring; h, cuticle; i, nucleus of ovum; /, vulva; k, blind end of pos- terior ovary; /, egg; m, beginning of the intestine; n, one of the cells of the wall of the intestine ; o, rectum ; p, anus ; q, one of the caudal glands ; r, flex- ure in anterior ovary; s, spinneret. SPILOPHORA, Bastian, 1865. Fig. 5. Spilophora canadensis, n. sp. Side view of male. a, one of the lips ; b, dorsal pharyngeal tooth partly exserted ; c, pharynx ; d, base of the pharynx ; e, lumen of the oesophagus ; /, nerve cells ; g, nerve- ring; h, excretory pore; i, chitinous valve of the cardiac bulb; /, one of the two lateral, longitudinal rows of cuticular markings; k, lumen of the intes- tine; I, renette cell; m, nucleus of renette cell; n, cell accessory to the renette cell ; o, blind end of single testis ; p, point in the cuticle where the striation is reversed ; q, vas deferens ; r, one of the spicula ; s, anus ; /, one of the caudal glands; u, spinneret. MICROLAIMUS, de Man, 1880. Fig. 6. Microlaimus fluviatilis, n. sp. I, lateral view of female; II, head of the same. a, Mouth opening; b, one of the six cephalic papillae; c, one of the four cephalic setae; d, one of the small pharyngeal teeth; e, excretory pore; /, spiral amphid; g, oesophagus; h, nerve-ring; i, cardiac bulb; /, preliminary portion of the intestine ; k, renette cell ; /, body cavity ; m, lumen of intestine ; n, one of the cells of the intestine; o, anus; p, flexure in posterior ovary; q, uterus ; r, blind end of posterior ovary ; s, one of the three caudal glands ; t, spinneret; uu, eggs; v, vulva; w, cuticle. TRIPYLA, Bastian, 1865. Fig. 7. Tripyla lata, n. sp. Lateral view, male specimen. a, cephalic seta; b, one of the three lips; c, amphid; d, spermatozoa; e. spermatocytes in anterior testis ; /, posterior extremity of the oesophagus ; g, nerve-ring; h, cuticle; i, oesophagus; /, lumen of oesophagus; k, intestine; /, spermatocytes in posterior testis ; m, one of the numerous ventral male papillae ; n, vas deferens ; o, retractory muscle of spiculum ; p, one of the spicula ; q, lumen of the intestine ; r, duct of one of the caudal glands ; s, caudal gland ; t, spinneret. FREE-LIVING FRESH-WATER NEMATODES Fig. 6. Microlaimus fluviatilis, n. sp. Fig. 7. Tripyla lata, n. sp. PLATE III. QO NORTH AMERICAN PLATE IV. ' TERATOCEPHALUS, de Man, 1876. Fig. 8. Tcratocephalus cornutus, n. sp. I, lateral view of a female; II, lateral view of head, more highly magnified; III, front view of head; IV, dorso-ventral view showing lips wide open; V, cuticle showing lateral field. a, one of the six movable, chitinous lips ; b, one of the four submedian cephalic setae ; c, amphid ; A, nerve-ring ; e, excretory pore ; f, organ of un- known significance ; g, cardiac bulb ; h, intestine ; i, anus ; /, rectum ; k, cu- ticle ; /, one of the cells of the intestine; m, lumen of the intestine; nn, flex- ures in ovary ; o, egg ; p, vulva ; q, blind end of posterior ovary ; u, terminus. ALAIMUS, de Man, 1880. Fig. 9. Alaimus simplex, n. sp. I, lateral view of a female; II, an- terior extremity, lateral view; III, posterior extremity of a male, lateral view. a, lip region ; b, pharynx ; c, amphid ; d, amphid, enlarged; e, group of spermatozoa at the posterior portion of the ovary; f, blind end of ovary; g, male supplementary papillae ; //, left spiculum ; i, terminus ; j, rudimentary submedian elevation or flap of the cuticle, indicating rudimentary bursa; k, egg ; I, vulva ; m, nerve-ring ; n, posterior extremity of oesophagus ; p, modi- fied cells of anterior portion of the intestine ; q, cuticle ; r, wall of the in- testine ; s, lumen of the intestine ; t, flexure in the single ovary. The arrangement of the ova and eggs may need a few words of ex- planation. The rounded blind end of the reflexed part of the single ovary is shown near the group of spermatozoa, e. The blind end contains a large number of oocytes of small size. These oocytes have more than doubled in size by J;he time they have reached the position, /. Henceforth they be- come arranged single file, always increasing in size until they pass the flexure, t. "At k a deceptive appearance is shown, inasmuch as the ripe ovum, k, has passed the flexure and in its passage to the uterus is pressing two of the unripe ova apart. This accounts for the apparent anomaly in relative size of the^ova in the vicinity of the flexure. PLECTUS, Bastian, 1865. Fig. 10. Plectus tubifer, n. sp. Male specimen, lateral view. a, lips ; b, papilla-like cephalic seta ; c, amphid ; d, anterior chamber of pharynx ; e, posterior chamber of pharynx ; /, lumen of the oesophagus ; g, nerve-ring ; h, excretory pore ; i, renette cell ; /, cardiac bulb ; k, vulva of cardiac bulb ; /, cardia ; m, lumen of intestine ; n, blind end of anterior testis ; o, spermatocyte ; p, junction of testes; q, blind end of posterior testis; r, be- ginning of vas, deferens; s, spermatozoon; t, male glands; u, one of the cau- dal glands; v, anterior of the three tubular supplementary organs; w, spicula; x, anus; y, one of the nine male papillae; z, spinneret. FREE-LIVING FRESH-WATER NEMATODES Fig. 8. Teratocephalus cornutus, n. sp. Fig. 10. Plectus tubifer, n. sp. PLATE IV. 92 NORTH AMERICAN PLATE V. ACHROMADORA. Fig. II. Achromadora minima, Cobb. I, lateral view of a female; II, lateral view showing cuticular markings; III, lateral view of head. a, cephalic papilla; b, cephalic seta; c, one of the ribs of the pharynx; d, dorsal pharyngeal tooth; e, sub-ventral (?) pharyngeal tooth; f, pharynx; g, cuticular markings ; h, amphid ; i, nerve cell ; /, nerve-ring ; k, spinneret ; /, excretory pore ; m, flexure of ovary ; n, one of the caudal glands ; o, blind end of posterior ovary; p, anus; q, intestine; r, vulva; s, one of the gran- ules of the intestine ; t, egg. DORYLAIMUS, Dujardin, 1845. Fig. 12. Dorylaimus fecundus, n. sp. Side view of head and tail of female, and tail of male. a, spear or onchus; b, one of the six anterior cephalic papillae; c, one of the six posterior cephalic papillae ; d, guiding ring of the spear ; e, oeso- phagus ; /, intestine ; g, rectum ; h, anus ; i, one of the anal muscles ; ;', one of the four lateral caudal, innervated papillae ; k, cuticle ; /, subcuticle ; m, mus- cular layer; n, wall of the intestine; o, one of the numerous oblique ejacu- latory muscles; p, one of the numerous ventral male papillae; q, ejaculatory duct ; r, one of the two preanal papillae ; s, retractor muscle of one of the spicula ; t, muscular layer ; u, right spiculum ; v, right accessory piece. IRONUS, Bastian, 1865. Fig. 13. Ironus americanus, n. sp. I, anterior extremity, lateral view, oral organs everted: II, same, more highly magnified; III, anterior extremity of a specimen about to moult, showing two sets of oral organs, the anterior set in process of being replaced by the posterior; IV, posterior extremity of a female, lateral view. a, one of the three chitinous oral teeth ; b, cephalic papilla ; c, cephalic seta; d, amphid; e, pharynx; /, anterior group of minute pharyngeal teeth; g, posterior group of pharyngeal teeth ; h, oesophagus ; i, lining of oesopha- gus ; /, nerve-ring ; k, intestine ; /, anus ; m, base of the tail ; n, terminus. ONCHOLAIMUS, Dujardin, 1865. Fig. 14. Oncholaimus punctatus, n. sp. Lateral view of head and tail of male specimen. a, terminal flaps of lips ; b, lip ; c, cephalic papilla ; d, one of the papilla- like cephalic setae; e, right submedian onchus; /, left submedian onchus; g, wall of pharynx; h, intestine; i, ejaculatory duct; /, one of the spicula; k, dorsal onchus ; I, amphid ; m, duct of oesophageal gland leading into onchus ; n, rectum ; o, beginning of the oesophagus ; p, anus ; q, lining of the oesopha- gus; r, one of the caudal glands; s, one of the two male papillae; t, ducts of the caudal glands; u, spinneret. FREE-LIVING FRESH-WATER NEMATODES 93 Fig. 11. Achromadora minima, Cobb Fig. 12. Dorylaitnus fecundus, n. ap. A Fig. 13. Ironus americanus, n. sp. Fig. 14. Oncholaimus punctatus, n. ip. PLATE V. 94 NORTH AMERICAN PLATE VI. TRILOBUS, Bastian, 1865. Fig. 15. Trilobus longus, (Leidy), Bastian. I, male specimen, lateral view; II and III, head of the same, lateral view; IV, head, dorso-ventral view; V, VI, and VII, enlarged views of the ventral supplementary organs. a, lateral cephalic seta ; b, cephalic papilla ; c, submedian cephalic setae ; d, pharynx; c, amphid; /, anterior pharyngeal tooth; g, posterior pharyngeal tooth ; h, oesophagus ; i, nerve-ring ; /, excretory pore ; k, nerve cells ; / gland- ular (?) organs; m, lumen of intestine; n, blind end of anterior testis ; o, testis; p, junction of testes; q, blind end of posterior testis; r, vas deferens; s, anterior male supplementary organ of the anterior series ; t, anterior sup- plementary organ of the posterior series ; u, spicula ; v, accessory piece ; w, caudal gland ; x, anus ; y, terminus ; z, nerve ending of papilla of the supple- mentary organ. DOLICHODORUS, nov. gen. Fig. 16. Dolichodorus heterocephalus, n. g., n. sp. I, nearly side view of a female; II, lateral view of surface of head, more highly enlarged; III, sagit- tal section of head; IV, dorso-ventral view of head; V, front view of head; VI, side view, posterior extremity of male ; VII, ventral view of posterior extremity of female; VIII, ventral view of posterior extremity of male. a, papilla ; b, cephalic organ of unknown significance ; c, spear ; d, base of spear; e, median bulb; /, nerve-ring; g, excretory pore; h, cardiac swelling; t, intestine ; /, anus ; k, lateral caudal pores ; I, terminus ; m, blind end of pos- terior ovary ; n, ovary ; o, left spiculum ; p, accessory piece ; q, distal end of Accessory piece ; r, left flap of bursa ; s, terminus of male ; t, ovum ; u, sper- matozoa ; v, vaginal muscles ; w, uterus ; x, vulva ; y, anus. CYATHOLAIMUS, Bastian, 1865. Fig. 17. Cyatholaimus truncatus, n. sp. I, side view of a female ; II, side view of head ; III, front view of the same head ; IV, ventral view of anal region of male; V, lateral view of the same; VI, lateral view in the middle of the body showing cuticular markings and pores. a, submedian cephalic seta ; b, labial papillae ; c, amphid ; d, dorsal tooth ; e, lateral cephalic seta ; /, one of the twelve ribs of the vestibule ; g, small submedian pharyngeal tooth ; h, base of the pharynx ; i, ejaculatory duct ; /, intestin* ; k, one of the four male pre-anal supplementary organs ; I, one of the spicula; m, anal muscles; n, one of the accessory pieces; o, nerve-ring; p, one of the cells of the intestine ; q, lumen of the intestine ; r, anus ; s, blind end of reflexed ovary; /, egg; u, vulva; v, flexure in anterior ovary; w, junction of the ovary and uterus; x, pores in the cuticle; 3;, one of the three caudal glands; z, male gland (?). FREE-LIVING FRESH-WATER NEMATODES i /c I Fig. 16. Dolichodorus heterocephalus, Fig. 17. Cyatholaimus truncatus, n. sp. n. g., n. sp. PLATE VI. 96 NORTH AMERICAN PLATE VII. MESOMERMIS. Fig. 18. Mesomermis virginiana, n. sp. Lateral view of head and tail. a, mouth opening; b, one of the anterior rows of cephalic papillae; c, one of the posterior row of cephalic papillae ; d, pharynx ; e, exterior of am- phid; /, interior of amphid; g, oesophagus; h, innervated papilla; , gland- ular cephalic organs; /, nerve-ring; k, lumen of oesophagus; /, intestine; m, ejaculatory duct ; n, body cavity ; o, oblique copulatory muscles ; p, one of the submedian supplementary organs; q, one of the median supplementary or- gans; r, spicula; s, one of the median post-anal supplementary organs; t, final submedian supplementary organs; u, submedian supplementary organ. ETHMOLAIMUS, de Man, 1880. Fig. 19. Ethmolaimus americanus, n. sp. Lateral view of a female. a, lips ; b, minute dorsal and ventral pharyngeal teeth ; c, one of the four cephalic setae; d, amphid; e, pharynx; /, nerve-ring; g, excretory pore; h, nerve cells; \, cardiac bulb; j, beginning of the intestine; k, renette cell (?); /, beginning of main portion of the intestine; m, one of two pairs of unicellular organs of unknown significance; n, cuticle; o, one of the cells of the intestine; p, subcuticle; q and r, body cavity; s, vulva; t, nuclei of one of the muscle cells ; u, spinneret ; v, one of the caudal glands ; w, anus. MONHYSTERA, Bastian, 1865. Fig. 20. Monhystera sentiens, n. sp. I, side view of a female; II, side view of head of the same; III, side view of posterior extremity of a male. a, pharynx ; b, submedian cephalic seta ; c, lateral cephalic seta ; d, sper- matozoon ; e, amphid ; /, lining of oesophagus ; g, oesophagus ; h, subcephalic setae; i, lumen of intestine; /, nerve cells; k, nerve-ring; /, striated lip re- gion; m, left spiculum; n, glandular structure associated with amphid; o, blind end of single ovary; pp, the three caudal glands; q, anal muscles; r, spinneret: s, beginning of intestine; t, anus; u, one of the cells composing the intestine; v, vulva; w, egg, the spermatozoa "d" being outside of the egg '''"; x, egg in synapsis ; y, vaginal glands ; z, ovum. ONCHOLAIMELLUS, de Man, 1886. Fig. 21. Oncholaimellus heterurus, n. sp. I, side view of head ; II, ven- tral view of head; III, side view of tail end of male; IV, ventral view of anal region of male. a, excretory pore; b, submedian cephalic seta; c, pharynx; d, left flap of bursa; e, oesophagus; /, left spiculum; g, accessory piece; h, amphid; , male post-anal seta and papilla; j, lateral seta; k, spinneret; I, thin lips. FREE-LIVING FRESH-WATER NEMATODES a b Fig. 18. Mesomermis virgimana, n. sp Fig. 20. Monhys'tera sentiens, n. sp. Fig. 21. Oncholaimellus he ,n, PLATE VI I. n " sp " 98 NORTH AMERICAN PLATE VIII. CEPHALOBUS, Bastian, 1865. Fig. 22. Cephalobus sub-elongatus, n. sp. Lateral view of a female. a, lips ; b, pharynx ; c, anterior portion of oesophagus ; d, posterior ex- tremity of anterior portion of oesophagus; e, nerve-ring; /, cardiac bulb; g, beginning of intestine ; h, one of the cells of the intestine ; i, lumen of the intestine ; /, excretory pore ; k, cardiac valve ; I, renette cell ; m, flexure in single ovary; n, cuticle; o, ovary; p, spermatozoon in uterus; q, vulva; r, nucleus in ovum; s, body cavity; t, anus; u, ripe ovum; v, unripe ovum; w, oocyte; x, blind end of ovary; y, rectum; z, terminus. 5k- BASTIANA, de Man, 1876. %' , Fig. 23. Bastiana exilis, n. sp. Lateral view of a male specimen. a, one of the six cephalic papillae; b, one of the posterior set of four submedian cephalic setae ; c, one of the anterior set of six cephalic setae ; d, oesophagus ; e, cervical seta ; /, amphid ; g, one of the cells of the intestine ; h, one of the numerous male supplementary organs ; i, blind end of the two testes; j, nerve-ring; k, posterior extremity of oesophagus, (pseudo-bulb); /, left spiculum; m, cuticle; n, spermatozoon; o, anal muscle; p, treminus; q, vas def erens ; r, intestine. MESOMERMIS, Dady. Figure 24. Mesomermis Virginia n. sp. Neck and head of the same species shown in figure 18, showing how the deteriorated oesophagus changes rather gradually into the intestine. a, mouth-opening ; b, one of the anterior row of cephalic papillae ; c, one of the posterior row of cephalic papillae; d, pharynx; e, exterior of amphid; /, interior of amphid; g, oesophagus; h, innervated papilla; i, glandular cephalic organs; j, nervering; k, lumen of oesophagus; /, intestine. APHANOLAIMUS, de Man, 1880. Fig. 25. Aphanolaimus spiriferus, n. sp. I, lateral view, anterior ex- tremity of a female; II, lateral view, posterior extremity of a female; III, lateral view of head, more highly magnified; IV, one of the male supple- mentary organs ; V, lateral view of posterior extremity of male. a, mouth opening ; b, amphid ; c, lumen of oesophagus ; d, pigmented eye- spot (?); e, intestine; /, nerve-cell; g, rectum; h, nerve-ring; i, anus; k, oesophagus ; /, caudal gland ; m, duct of one of the caudal glands ; n, gland- ular body at base of neck; o, spinneret; p, ejaculatory duct; q, intestine; r, anterior end of cloaca ; s, right spiculum ; t, backward pointing accessory piece; u, nerve-cells (?) ; v, one of the numerous male supplementary organs. FREE-LIVING FRESH-WATER NEMATODES 99 Fig. 22. Cephalobus subelongatus, n. sp. Fig. 24. 2S 92.7 following average formula: 2 - 4 mm -* 2.1 2.6 3. 3.2 2. * This formula, which is now coming into more general use, is simply a decimal method of stating concisely the necessary measurements. The formula is fully explained in the appendix, r. 184. 13 2(S-S.434) THE MONONCHS which corresponds very closel} with that of the type species of the genus, M. truncatus Bastian, and espec- ially with M. papillatus Bastian. Skin or Cuticle Strics. While the skin of these nemas usually described as smooth and without striations, yet minute trans- verse striae are probably always present, though difficult of resolution except in the new species reversus and similis. Using a good objective of the highest power under favorable conditions, I have almost invariably been able to see these striae, and as my examinations have embraced the great majority of the known species, it seems probable that any specimen will reveal them if examined with sufficient care. These transverse striae, all alike on a given specimen, are never sufficiently marked , , FIG. 2. Female of a typical mononch, par Mononchus longi- , caudatus, a syngonic form. This individ- ual had been feast- ing on other nemas, t h e remains of which are shown in- side the intestine. Only the anterior half of the sexual organs can be seen in the illustration; an entirely similar branch is hidden on account of the coiled attitude of the body. The lettering of the illustrations is similar throughout and is explained at the bottom of page 129. The anatomy and histology o f various newly dis- covered features are shown: GJsophageal glands (gl. sal.), the pore mlr Inf through which the glands empty into -. theossophagus (par.), syngonic sperm j, (spm.), formation of "" polar body (ov.frt.), ingested protozoon (ing.), etc. to disturb the plain, even contour of the body. It is rarely possible to CUTICLE AND MOULTING (8.8.435)133 resolve the striae into components ; occasionally, however, they are resolv- able into rows of excessively fine dot-like elements, as for instance in bathybius, reversus and incurvus. Lateral wings to the cuticle are almost unknown, and the striae are not perceptibly altered on the lateral fields; papillatus and macrostoma furnish a slight exception to this rule. Though the muscles of the body wall are relatively powerful, their attachments to the subcuticle are not a conspicuous feature ; hence longi- tudinal striae due to this cause, though of rather common occurrence, are not very readily observed. There are no longitudinal striations in the cuticle proper. This apparent complete absence of dermal markings often imparts a glassy appearance to living mononchs when examined casually under the microscope, an effect that is heightened by the fact that the colorless body wall is, as a rule, of more than average thickness. Despite their rather thick cuticle, mononchs are very flexible. They coil and un- coil themselves with facility, a useful gift in a struggle with active prey. Moulting. From researches on a considerable variety of genera, Mau- pas concluded that nematodes undergo four moults, and that, correspond- ingly, the life of each individual is divided into five periods. He exam- ined no mononchs. The accompanying sketch of a portion of the pharynx of a moulting Monochus brachyuris, from Arlington, is therefore of interest, as indicating that this specimen had yet to moult three times ; and since it was already half-grown (0.8 mm. long) it is fair to presume it had already moulted once, although of course there is no proof of this. The sketch shows four successive dorsal onchi, numbered in chronological order, each the represent- ative of a separate cuticle. The fourth onchus is in a very lessive 'dorsal rudimentary state. This record accords with the observa- :eth> *' 2> 3 ' 4 ' tions of Maupas, and indicates the probability that mononchs also moult four times. Strength and Activity. Various features of the cuticle and body- muscles seem to stamp the mononchs as powerful nemas, and when they are taken from their natural haunts and placed in a glass of water for examination, their active serpentine movements fully justify the infer- ence. Though less agile than species belonging to some other genera, they are anything but sluggish. The movements of the anterior extremity are especially striking, a certain suppleness of neck enabling them to dart the head suddenly here or there in almost any direction, a faculty enabling them with ease to capture their prey, even though it be active. Nemas Sometimes Float Distribution by flotation. Ditlevsen notes a very interesting trait of his Mononchus spectabilis, namely, that of floating on the surface of water. A number of free-living nemas belonging to other genera are 134(3.3.436) THE MONONCHS known to have this faculty, which is due to repulsion between the cuticle and water ; de Man found it to exist in the case of Oncholaimus viscosus, and the writer has observed it in the case of the larvse of Diplogaster aerivora, although a second larval form of this same species does not exhibit the property, nor do the adults. Ability to float is known also of a number of other species, and, as Ditlevsen's observations show, is not absent in the genus Mononchus. Whether flotation plays any part in the economy of such nemas is not known with certainty. Floating on the surface of moving water, nemas would doubtless sometimes be quickly and widely distributed, and it is therefore easily conceivable that flotation has some definite bearing on the life history of species exhibiting it. The surface of a mononch seems almost *' Jfc ' >^^-^H -^T^ ' entirely destitute of setae and papillae, if we except those on the lips. Neverthe- less, future researches will probably re- veal superficial nerve-endings hitherto overlooked. In rare instances a few fairly well-developed setae occur on the tail, as in the case of M. sigmaturus; papillae also occur sparingly on the tails of the males of various species, and near the vulva on the females of a number of species. No the lips are nearly closed, but the dor- pores are known tO OCCUr in the CUticle, Si", Sr~'SS except, of course, the spinneret pore, and of papilla: are seen to good advantage, the pore observed near the nerve-ring and to be the renette pore. General Form of Body Neck and Head. The various mononchs are considerably alike in external form. In front the body tapers but little; the neck is nearly always more or less cylindroid, and almost invariably ends in a head not set off from the neck in any way, though there is usually a slight expan- sion at the lip-region, due to the strong development of the labial papillae. Tail and Spinneret. The posterior portion of the body usually tapers from some distance in front of the anus, but in the pre-anal region the diminution is slight and very gradual. The tail may be either simply conoid, or first conoid and then cylindroid, and usually ends in a spin- neret, though in about one-fourth of the species the caudal glands and spinneret are absent. When the tail is conoid the spinneret is usually a simple structure, whose existence is indicated mainly by the fact that the terminus is sub-truncate in form, and presents an inconspicuous axial, or sub-dorsal, or sub-ventral pore. This form of spinneret appears to be entirely unarmed, though inconspicuous innervations probably occur. LABIAL APPENDAGES (S. S. 437) 135 When the posterior portion of the tail is cylindroid, the terminus is usually almost imperceptibly expanded, and the spinneret is then some- what differently developed, and is usually armed with obscure, innervated, submedian papillae or setae. Head Lips. In the view usually obtained the six lips appear to be more or less confluent, and if it were not for their papillae it would be difficult to count them ; but when thrown apart, an attitude in which, x 1000 however, they are seldom seen, they are more easily ,, J J J ric. 5* opinncret ox counted, since in this attitude the refractive "cerat- '"Ss^whos*' contrac- inous" internal elements of the lips are separated Jon ^open s w the se spinneret from each other and more readily distinguishable, as shown in figure 1. When closed, these six, broad, flat lips meet together in such a way that the star-shaped mouth opening usually lies in a slightly depressed area on the middle of the front of the head. In some species the inner walls of the lips are strongly "ceratinized," and may be developed into six rather definite, retrorse, subacute points, which, in assaults on other animals, serve as grappling hooks, and act in opposition to the dorsal tooth of the pharynx. Labial papilla. Each lip is supplied with at least two, usually more or less conical, innervated papillae; one on the outer margin and somewhat outward pointing, the other situated about half way between the outer papilla and the centre of the head, and forward-pointing. The front of the head therefore presents two circlets of papillae, one on its outer mar- gin, and one more closely surrounding the mouth-opening, as shown in figures 1 and 4, and many others. These papillae may be so flat as to play no conspicuous part in the external conformation of the head, or they may be conical and raised, so as to give to the front of the head a more or less angular contour. The papillae are slightly mobile, and hence vary somewhat in appearance at different times on the same specimen, a matter depending on the attitude of the lips. Drowned specimens with relaxed lips present a slightly different appearance from those that have been fixed for examination by means of chemicals. Some of the innervations that frequently occur on the head near the lips may have special functions. Structurally they are sometimes indis- tinguishable from the subordinate labial papillae. The species figures show the location of some of these innervations. One pair of them is very near the amphids the only nerves so far observed to be definitely associated with the amphids. These particular papillae are so uniform in their' occurrence that it seems likely they have a special function, con- nected with the use of the amphids. 136 tactile and partly excitatory in *; function, and act as the comple- J; ^jacSatM^duct ments of the vulvar papillae of the r ; ^"fetory duct female. There is no bursa. The series of oblique copulatory mus- cles is always coextensive with the series of supplementary or- s - three anal R lands gans. The rather short testes seem to be invariably two in number and are outstretched in opposite directions. The spermatozoa of males are minute and present a more or less vermiform nucleus. Self -Fertilizing Females; Syngonism Males Rare. Conjugation of Syngonic Gametes. No trait of mon- onchs is more interesting than the capacity of the female to reproduce without the intervention of a male by a peculiar sort of hermaproditism called syngonism. Of most of the species no males are known; in the remaining species, almost without exception the males are very scarce, and only in exceedingly rare cases are they present in anything more than small numbers. Usually hundreds, and even thousands, of speci- mens may be examined without the discovery of a single male. How then do the females reproduce? The answer is singularly interesting, for, as already explained, the females fertilize their own eggs by means of spermatozoa which they themselves produce in the same gonad. In the mononchs these spermatozoa produced by females are so exceedingly minute that they have hitherto escaped notice (fig. 2). Notwithstanding its small size, the syngonic sperm cell appears to be functional. It enters the egg, expands, and approaches the nucleus of the egg, which mean- while throws off polar bodies and later proceeds with segmentation. Observations have not yet extended beyond this point, but it saems alto- 150< S -S.4S2) THE MONONCHS gether likely that these minute spermatozoa produced by mononch syngones act in what would be called a normal manner, and as the sperma- tozoa are known to do in other syngonic nemas in which they are of much larger size, e. g. Rhabditis. Abundance; Distribution Frequency of Mononchs. Long ago Biitschli declared mononchs to be among the commonest of nemas, an assertion that has been corrobo- rated by all investigators in this field, hardly any of whom have failed to note a number of species, occasionally new ones. Our knowledge of the genus has been augmented in this way by de Man, Micoletzky, Ditlevsen, Steiner, Hofmanner, Menzel, Daday, and the writer, until at the present time about sixty species are known. Doubtless this number will be very largely increased by future researches. Geographic Distribution. Variety of Habitat. Mononchs are found in all the habitable regions of the world. They inhabit the soils and fresh waters of every clime, occurring even at great depths in lakes and at very high altitudes on mountains. While we have only just begun to learn the details of their geographic distribution, it is already manifest that some species are cosmopolitan. Several species occur both in Europe and in North America, and a few of these same species are known also from Australia. Considering the small number of observations hitherto made along this line, it seems safe to predict that many of the species will be found to be cosmopolitan. Some species adapt themselves to sur- prisingly varied conditions. Mononchus longicaudatus, for instance, is known from the tropics, from temperate regions, and from very cold regions, and inhabits both soil and fresh water. Another species, Mon- onchus brachyuris, is known both from warm springs and from cold Alpine lakes. Abundance in Arable Soil. Mononchs occur in great numbers in arable soil. On one occasion the writer estimated that at least thirty millions of mononchs per acre were present in the top six inches of a field of maize in New Jersey, and the actual number present may have been much greater. They are regularly present in practically all arable land of a sandy or loamy nature. The very numerous introductions of living plants into the United States, through the agency of the Office of Seed and Plant Introduction of the Department of Agriculture and other agencies, has brought about simultaneously the introduction of many species of Mononchus. Nemas existing in the soil about the roots of introduced plants are often placed under favorable conditions for propagation in this country. It is therefore certain that an unusual variety of mononchs exists in the soils of the United States. GENUS MONONCHUS (S.S.453)i5j Interplay of Organisms. There are regions where certain nematode diseases of crops are very destructive, while other regions, the climate and soil conditions of which are apparently similar, suffer but little, or at least to a lesser degree, so far as we know. In such cases it is permis- sible to suppose that the nematodes in the area where the lesser damage is done are held in check by some as yet unknown agent. Is it not pos- sible that the mononchs play some such role as this, and that just as cer- tain insects hold other insects in check, so certain nemas hold other nemas in check? We know relatively little about the life history of most of the mon- onchs, and as yet very little about the possibility of controlling their growth. One species, Mononchus longicaudatus, occurs at certain times in almost inconceivable numbers in the sand of the slow filter beds of the water works of cities. Near the end of the period of use the top layers of the sand in these filter beds sometimes become in reality a huge culture of this species. The observations suggest at least the possibility of culti- vating this species on a large scale, should it prove desirable to do so. The discovery that the genus Mononchus is very large and to a con- siderable extent composed of common and cosmopolitan species that feed upon injurious plant-infesting organisms, suggests so many new lines of research in soil biology as to make it desirable that a clear and connected account of the members of the genus be available to investigators. This need is increased by the fact that the literature is a scattered and frag- mentary one, difficult to assemble. To these facts it must be added that most of the new observations herein recorded have been made upon species previously unknown. II GENUS MONONCHUS BASTIAN, 1866 This genus is composed of non-marine, free-living nemas, with naked cuticle and obscure amphids, and having a plain oesophagus preceded by a broad that is, non-tubular pharynx, armed with 1 to 3 more or less immobile teeth of which the dorsal is largest, and supplied with 6 power- ful papillated lips. Ovaries reflexed, usually two. Testes two, out- stretched ; spicula two, equal, simple, as are their small accessories ; there is a pre-anal ventral row of supplementary organs. GENERA SIMILAR TO MONONCHUS, WITH DISTINGUISHING CHARACTERS Oncholaimns Anonchus Microlaimtts Irottus Nannonchus Oionchus Mononchtilus Marine; sometimes found in brackish soils. Has cephalic setse. Has spiral amphids, and cephalic setse. No thick muscular lips; amphids circular. Pharynx tubular; teeth movable radially. Has spiral amphids and cephalic setae. Pharynx filled by single tooth, which is really spear-like. Quite similar. Has much larger (ventral) spinneret; strongly developed lateral fields; smaller pharynx; female organ single. 152 (s-s- 45-0 THE MONONCHS Mononchus Bastian, 1866 ay in pharynx or higher, usually massive MONONCHUS Cobb; Subgenera and Species 1. MONONCHUS DORSAL TOOTH midw . _ , Tooth not opposed by denticles; subg. type, M. truncatus Bast.; pharynx about 2 to 3 times as long as wide, goblet-shaped or ellipsoidal; wall smooth or transversely striated; spinneret usually present; males of about half the species known; female organs double (except monhystera) Dorsal tooth faced by 2 ventrally submedian teeth Teeth retrorse (tridentatus de Man 1876) Teeth not retrorse Tail conoid, then cylindroid; body 7 mm. long (rex Cobb 1904) Tail simply conoid; body 3 mm. long or less Spinneret and caudal glands absent exilis n. sp. Spinneret and caudal glands present . . Contour of the head angular; labial papillae 16 radiatus n. sp Contour of the head rounded; labial papillae 12 Pharynx longer than the head is wide palustris n. sp. Pharynx only as long as the head is wide teres n. sp. Dorsal tooth not faced by submedian teeth Ovary 1; pharynx not much longer than wide monhystera n. sp. Ovaries 2; pharynx toward twice as long as wide Tail simply conoid, 8 per cent or less Spinneret none Pharynx over half as wide as the head vorax n. so. Pharynx not over half as wide as the head Length about 1 mm.; tooth midway, small, digitate parvus de Man 1879 Length 1.5 to 2 mm.; tooth beyond midway, massive papillatus Bastian 1866 Spinneret present Body 2 mm. long Form of the tail regular Form of the tail somewhat irregular Body 3 to 4 mm. long Tooth midway, amphids a little behind the lips maior Cobb 1893 11 Tooth and amphids at the base of the lips gerlachei de Man 1904 12 Tail conoid, then cylindroid, about 10 per cent or more (Esophagus 15 per cent fovearum (Dujardin) Bastian '66 13 intermedius Cobb 1893 tenuicaudatus Stefanski 1914 obtusus n. sp. tunbridgensis Bastian 1866 longicaudatus Cobb 1893 2. SPORONCHULUS (Esophagus 22 per cent or more Buccal cavity toward 2 times as long as head is wide Spinneret armed with 2 very small setae megalaimus n. sp. Spinneret not armed with setae macrostoma Bastian 1866 Buccal cavity only about half as long as head is wide Labial papillae setose Labial papillae, at least the outer, not setose Pharynx 54 as wide as head; body 1.5 mm. long Pharynx */ 2 as wide as head or more; body 2 to 3 mm. Cavity about 2 times long as wide; tooth acute truncatus Bastian 1866 Cavity about 3 times as long as wide; tooth sub-acute Inner labial papillae large; tail sub-conoid., dadayi Micoletzky 1904 Inner labial papillae normal; tail finally cylindric Tooth opposed by numerous denticles on opposite wall Arrangement of the denticles irregular; characters otherwise as in Mylonchulus; subg. nov. SPORONCHULUS; type S. dentatus n. sp. The tooth behind midway; spinneret present; anus at 92; 'f recessus n. sp. The tooth in front of midway; no spinneret; anus at 96; Denticles about 20; pharynx half as wide as the head; T dentatus n. sp. Denticles about 50; pharynx one-third as wide as the head Arrangement of the denticles orderly Denticles along a ventral, longitudinal pharyngeal rib; subg. PRIONCHULUS Cobb; type Pr. muscorum (Dui.) Bast.; pharynx ellipsoidal, about 2 times long as wide; males of one species known; female organs double; no spinneret Eggs punctate or echinulate punctatus Eggs not punctate or echinulate Length 2.5 to 3.4 mm.; vulva at 65 per cent; anus at 94 per cent Width 3.6 per cent; denticles forward pointing muscorum (Duiardin) Ba Width 2.3 per cent; denticles inward pointing longicollis n. sp. Length 4 mm.; vulva at 55 per cent; anus at 97 per cent spectabilis Ditlevsen 1911 Denticles in transverse rows on 2 sometimes confluent, sub- median, rasp-like areas, often with 2 very small sub- median teeth at their bases; subg. MYLONCHULUS Cobb; type M. minor Cobb; pharynx goblet-shaped, tooth more or less arcuate; smaller species of which iecurrens n. sp. 21a 21c 3. PRIONCHULUS sp. '66 23 24 25 KEY TO GENUS MONONCHUS (S. S. 455) 153 the males are unknown (except tennis) ; female organs double (except index and reverses) ; spinneret present (except similis) Ovary 1; tail rapidly diminished, then digitate Vulva behind the ovary; denticles normal Vulva in front of the ovary; denticles few Ovaries 2; tail not digitate (Ex. perhaps sigmaturus) Dorsal tooth somewhat digitate, relatively small Refractive ring about pharynx in front of tooth Refractive ring about pharynx not prominent Dorsal tooth massive, not digitate Head rounded, denticles in about 12 rows Head truncate, denticles in 2 to 6 rows Rows of denticles 2 Rows of denticles 4 to 6 Denticles about 4 rows; spinneret small Denticles about 6 rows; spinneret larger Tail bent ventrally near the middle Caudal setae none ; tail conoid Caudal setae (3 pairs) present; tail not conoid Tail arcuate or straightish Width of adults 2.3 per cent Width of adults 2.7 per cent or more 8audal glands and spinneret absent audal glands and spinneret present Eggs thick shelled Eggs thin shelled Buccal striae faint if any; anus 94 to 96 per cent Species aquatic Species not aquatic Buccal striae more pronounced; anus 98 per cent Spinneret finally dorsally recurved.. Spinneret not dorsally recurved DORSAL TOOTH and others small, basal or nearly so (Exc. 44) Teeth retrorse, small, basal, exceptionally midway; subg. ANATONCHUS Cobb; tvpe A. tridentatus de Man; large species with roomy elongated pharynx and smallish retrorse teeth; tail long and usually becoming cylindroid; female organs double; males of most of the species known Body 2 to 4 mm.; teeth equal, midway; anus 90 per cent.... Body 5 to 6 mm.; teeth sub-basal; anus 80 to 85 per cent Submedian teeth equaling the dorsal; body 6 mm Submedian teeth smaller than the dorsal; bodv 5 mm Teeth not retrorse, small, 9r even minute; subg. IOTONCHUS Cobb; type I. gvmnolaimus Cobb: large species with roomy elongated -harynx having longitudinal ribs; tail rather long, and often slender; males of more than half the species known: female organs double or single; most species with spinneret Ovary single; 1 to 3 rudimentary basal teeth Tail digitate; 3 sub-equal vestigial teeth Tail not digitate- 1 dorsal tooth, remainder faint or none Posterior extremity setaceous Posterior ext-mity slender but not setaceous Pharynx as long as wide; few submedian denticles... Pharynx about 2 times long as wide; faint submedian teeth Amphid simnle; buccal wall thin, transversely striated Amphid duplex; buccal wall thick, not striated Ovaries 2; 1 t" 3 small, sub-basal teeth Body 4 to 7 mm.; tail finally cylindroid; 3 teeth Spinnerer present; lips rather plain Length 4 mm.; anus 90 per cent; the 3 teeth subequal Length 6 to 7 mm.; anus 80 per cent; submedian teeth smaller Spinneret none; lips striated lengthwise . . ._ Body 1 ti 4 mm.; tail conoid; 1 tooth, sometimes denticles Anus .-* about 86 per cent; tail conoid, or at last sub- cylindroid Lips not set off by constriction; onchi unequal or one Onchus with small companions; head rounded Onchus one only; head truncate; pharynx striated... Lips set off by a deep constriction; onchi three, equal Anus at about 94 per cent; tail simply conoid Dorsal tooth small, others basal, minute, indefinite. . . . Dorsal tooth distinct Buccal cavity half as wide as long: tooth sub-basal.. Buccal cavity as wide as long; main tooth basal Spinneret present Spinneret none 4. MYLONCHULUS index Cobb 1907 reversus n. sp. obtusicaudatus Daday 1901 brachyuris Biitschli 1873 denticulatus n. sp. sparsus n. sp. micrurus n. sp. incurvus n. sp. sigmaturus n. sp. subtenuis n. sp. subsimilis n. sp. obliquus n. sp. lacustris Cobb 1915 polonicus Stefanski 1915 minor Cobb 1893 brevicaudatus n. sp. japonicus n. sp. ANATONCHUS tridentatus de Man 1876 gracilicaudatus n. sp. dolichurus Ditlevsen 1911 6. IOTONCHUS digiturus Cobb 1893 trichurus n. sp. (bathybius Micoletzky 1913) gvmnolaimus Cobb 1893 consimilis n. sp. rex Cobb 1904 regius n. sp. bathybius Micoletzky 1913 similis Cobb 1893 fasciatus n. sp. studeri Steiner 1914 zschokkei Menzel 1913 brachylaimus n. sp. acutus n. sp. THE MONONCHS 1. M. exilis, n. sp. The cylindroid neck ends in a rounded head with a dis- tinctly expanded lip region. The large pyriform pharynx is armed with three sub- equal teeth. The wider anterior part of the pharynx is two-thirds as wide as the * head. The apices of the teeth are midway, 1.8 6.2 27. '78' 15 98.2 the dorsal one being a little the farthest for- 1.6 1.8 2. 2.3 \. m ward. Amphids somewhat behind the lips, 1.6 6. 24. -M- 38 98. but farther forward than the teeth, consisting 1.6' 1.8 2. 2.2 1.2 of somewhat rectangular markings one-fifth as wide as the head, longest in the transverse direction, and with the lateral and front margins plainer than the posterior. Lining of the oesophagus not so promi- nent as in most mononchs. Intestine greenish, finely granular, obscurely tessellated. Cardia long and plainly to be seen through the flat, colorless pseudo-bulb at the beginning of the intestine. The rectum has a thick lining of highly refractive ceratin, and is a prominent organ one and one-half times as long as the anal body- diameter. Terminus about one-fourth as wide as the base of the tail. The very broad vulva is only slightly elevated. Posterior sexual branch only two-thirds as long as the anterior. On the male there is a row of about 14 equidistant, rather closely approximated ventral ridges in front of the anus, extending forward a dis- tance equal to 3 tail-lengths. These do not bear any prominet papillae. The body is somewhat thicker in the region of these ridges. Spicula linear, uniformly 5 /j. in diameter when seen in profile, the proximal end being in no way distinguished from the rest of the shaft. The accessory pieces appear to rest rather closely against the distal halves of the spicula. Found about the roots of moss, Moss Vale, New South Wales, 1894. Examined in water after fixation with osmic acid. 2. M. radiatus, n. sp. The amphids of this rather small 3.3 9. 30. 95. .8 mir 2.2 2.8 2.8 2.3 2.2 but elegant species are minute and inconspicuous, about one- eighth as wide as the corresponding part of the head. The granules of the intestine are largest posteriorly, where they are about one-half as wide as the spinneret. The intestine is not tessellated. The tail is markedly arcuate, its spinneret about one-fifth as wide as its base. Anus very slightly raised. Caudal glands rather small, elongated. Sexual organs apparently double and symmetrically reflexed. Description derived from a single young specimen from a cranberry bog in New Jersey, U. S. A. Flemming solution to glycerine. Fig. 17.** 3. M. palustris, n. sp. Intestine 12 to 15 cells in girth, more or less distinctly "# J 2.7 8. 30. '62' 15 97. tessellated. Tail arc- jT 27s 27e 27? 1.9 > 1-4 IBra uate, its rather conoid spinneret about one-fifth as wide as its base. Caudal glands broad and saccate, their ampullae occupying most of the posterior half of the tail. The elongated eggs are about twice as long as the body is wide, and occur one at a time in each uterus. The rather small, tapering ovaries contain 8 to 10 ova arranged more or less irregularly. From a white cedar swamp, Jefferson County, Wis- consin, U. S. A. Feeds upon rotifers and probably upon other nematodes, which it appears to masticate (page 443, fig. 10). Sublimate to balsam. Fig. 18. ^* This decimal formula for nemas is explained in the appendix. ** The species figures have the same magnification throughout, so that the reader may guage the relative sizes. SUBGENUS MONONCHUS (S.S.457) 155 4. M. teres, n. sp. This comparatively small, simple form has 2 submedian teeth of equal size. Walls of the intestine with numerous granules of rather uni- form size, giving rise to a faint tessellation ; the granules such that 2 to 3 would be required to span one of the 3.9 12. 35. 60 Y 94. amphids. Tail rather strongly 3~4 37 375 372 2.^ ' " arcuate, its fairly well developed spinneret about one-fifth as wide as its base. Caudal glands somewhat elongated, their small but rather conspicuous ampullae nearly filling the posterior fifth of the tail. Description prepared from a single, more or less shrunken speci- men, found in the sphagnum of a pot in which blueberry plants were being cultivated. Bears a general resemblance to papillatus, but differs in the form of the pharyngeal teeth and of the terminus. Flemming solution to glycerine. Fig. 19. 5. M. monhystera, n. sp. Amphids not seen. Lining of the rectum and of the intestine rather distinct and refractive. Intestine only faintly tessellated, if at all. 3.3 9.7 27. '78 19 94 Tail arcuate . rather 37 37s 76 372 27s~ 1-1 M blunt, without spin- neret. From the rather conspicuous, more or less elevated vulva, the vagina, which is two-thirds as long as the body is wide and tubular, extends obliquely inward and forward. Nothing definite is known with regard to the eggs or the form of the ovary. Found about the roots of orange trees, Bahia, Brazil. Bears a general resemblance to M. papillatus, but has only one ovary. This species is nemativorous. Flemming solution to glycerine. Fig. 20. 6. M. vorax, n. sp. This voracious species has a large mouth cavity and the oesophagus is therefore at first slightly swollen. Intestine 12 to 20 cells in girth, not tessellated. The 2 .7 8. 27. >67' 22 92. terminus of the arc- 1.4 BE 2.1 2.3 2.7 2.6 1.6 uate tail is about one-seventh as wide as its base. The elongated eggs are about twice as long as the body is wide. Each ovary contains about 30 developing ova, arranged irregularly. Small sperm cells were seen in abundance at the flexure, in a condition indicating that the species is syngonic. Found in soil from a white cedar swamp in Wiscon- sin, and from a cranberry bog in New Jersey, U. S. A. This is apparently a voracious feeder on other nema- todes. Remains of Dorylaimus and Ironus were seen in the intestine. Resembles M. mac- mr t* -~fl \^~ft rnstoma, but the tail is conoid and has no spinneret. Sub- limate to balsam. Fig. 21. T. M. parvus de Man. De Man mentions the presence of minute teeth at the base of the pharynx, near the be- 3.1 - 9.5 29. *63< 93. ginning of the oesoph- 17 ^ ^ gTj; ^7 l.l n agus. Lining of the oesophagus well developed. Intestine apparently about 10 to 12 cells in girth, tessellated. Rectum somewhat shorter than the anal bodv-diameter. Tail arcuate; its terminus only about one-eighth a 156( s - s - 458 > THE MONONCHS wide as its base. An egg seen in the uterus measured 100 ^ in length. It is not certain that caudal glands are present. Knowledge of this species rests very largely on the observations of Dr. J. G. de Man, who says that it is an active species, common in sandy soils of the dune dis- tricts of Holland. Occurs also in Germany, according to Brakenhoff, whose speci- mens, however, have the dorsal tooth close to the lips instead of midway as in the type form. Fig 22, previous page (after de Man). 8. M. papillatus Bastian. Glands are present in the segments of the oesophagus, and are most strongly developed in the posterior half. The secretion of the glands co , 2 7 in the dorsal segment 3. 9.3 2b. *bl"-' 93. . . 2.6 3.5 3.8 4.3 2.4 pours into the lumen of the oesophagus through a minute pore near the middle of the neck, a short distance behind the nerve-ring. Under favor- able conditions lenses of the highest power show transverse striae to be interrupted on the lateral lines, where there are 2 ^ refractive longitudinal striations very close together. What appears to be an ordinary ventral renette pore is found a short xfso distance behind the nerve-ring. The writer's investigations prove this species to be syngonic. The longitudinal ribs of the pharynx, probably 3 in number, are a little more prominently developed than usual. Occasionally a subventral or submedian rib of the pharynx shows traces of most exceedingly fine denticles. Only the most careful examination of favorable specimens shows these denticles. The writer has never observed a denticulated ventral rib like that of muscorum, as mentioned by Menzel. A common, voracious, cosmopolitan, nemativorous species. Found in many parts of Europe and of the United States, and also in Hawaii, Australia, South America and Asia. Fig. 23. See also fig. 8. 9. M. intermedius Cobb. Truncate head having 6 lips, each with 2 papillae. The elongated-oval amphids are half as wide as the base of the lip. The rather long, goblet-shaped pharynx is half as long 2.5 7.4 24. '6i' 35 94. as the head is wide, and presents a mod- 2.4 2.4 2.8 3.3 2.4 erate-sized dorsal tooth two-thirds the way from the base to the lips. The intes- tine, whose commencement is marked by the presence of a pseudo-bulb, shows a rather indistinct tessellation. What appears to be a ventral renette pore occurs just behind the nerve-ring. The lateral fields are one-fourth as wide as the body. Caudal glands are present in the conical, arcuate tail. Spinneret almost pointed. Anus depressed, consequently conspicuous. Vulva conspicuous. The reflexed por- tions of the ovaries extend one-half way back to the vulva. Found about the roots of sugar cane, Harwood, Clarence River, New South Wales, Australia.. Examined in water after fixation with osmic acid vapor. 10. M. tenuicaudatus Stefanski. The lips are said to bear 6 large, spheroidal papillae. A transverse element is said to traverse the wall of the pharynx opposite ? ? 21. '50+* 94. the apex of the 4 - ^ dorsal tooth, and to bear 2 slightly curved projections. The oesophagus is muscular. At first the tail diminishes regularly in diameter, but presents 2 swellings in the posterior part. Found among algae, in the Rhone River, Switzer- land. This species is said to resemble M. macrostoma Bastian in the form of the buccal cavity, but to differ from that species in the details of the structure of the mouth, as well as in the form and length of the tail. Fig. 24, after Stefanski. \\\ ^O> X 750 SUBGENUS MONONCHUS (s. s. 459) 157 ii. M. major Cobb. Labial papillae of the inner row each with 3 (?) nerve- endings. Amphids slightly farther forward than the apex of the dorsal tooth, small. Lateral fields one-fifth as wide as the body. Intestine composed of rather small cells, 3.4 mm , snowing an .6 6. 19. '55 25 95. 2.6 2.9 -M- 45 1.5 indistinct tes- 2.3 2.9 2.8 2^ sellation. The eggs are probably less than twice as long as wide. Each of the 12 rather conspicuous, echinulate, mammiform accessory organs is situated on the posterior side of a transverse ceratinous ridge extending one-fourth the dis- tance around the body. The anterior two or three and the posterior one of these organs are smaller than the others. There are 2 pairs of ventrally submedian papillae, also inner- vated, on the anterior third of the tail, the posterior pair being near the end of the an- terior third, and the other pair half way be- tween- that point and the anus. There are other papillae faintly visible on the dorsal side of the tail and elsewhere (fig. 16). The fe- males of this species also present papillae near the vulva: 3 small, ventrally submedian papillae on each side of the body, one opposite the vulva, one a short distance in front of it and another a short distance behind it, and in addition a tandem series of 3 papillae, both in front of and behind the vulva, on the ventral line. The location and conformation of these papillae is shown in figure 12. Doubt- less the females of other species possess similar papillae. Fixed with osmic acid; examined in water. Found about the roots of plants, in damp soil, Moss Vale, New South Wales, Australia. Also about turnips in Tasmania. This species resembles the following. Fig. 25. 12. M. gerlachei de Man. Lateral fields about one-third as wide as the body. In transverse section the buccal cavity, though nearly round, is obscurely three- sided, and shows the existence of 3 small, longitudinal grooves in the wall of the 2. 5.2 18. '50' 33 92.5 _ 1.8 2. 2. 95.5 1.8 ? ? 3.7 2.3 pharynx, presumably so functioning as to increase the elasticity and mobility of the pharyngeal walls. What appears to be a renette pore occurs immediately behind the nerve-ring. Anal muscles are well developed in the female. Spic- ula arcuate, tapering both ways, about one and one-third times as long as the anal body-diameter, and in their widest part about one-sixth as wide as the corresponding portion of the body. The accessory pieces are about one-third as long as the spicula, relatively small and poorly developed, appearing to be parallel to them when viewed in profile. The 1 5g(S.S.460) THE M ON ON CHS pre-anal ventral row of supplementary organs is essentially the same as in major (fig. 16). According to Steiner's observations the number of supplementary organs in this species may at times be as great as that noted in major. Steiner calls atten- tion to the existence of a submedian row t> pre-anal papillae, lying on either side of the ventral row. The tail bears 3 pairs of papillae, one submedian or subventral pair near the anus ; a second subventral pair slightly behind the middle ; and a third dorsally submedian pair at the beginning of the final fourth of the tail. In the male the slightly conoid spinneret is one-sixth to one-seventh as wide as the base of the arcuate tail. The proportions are about the same as in the female, although the tail of the female is slightly longer and more slender, and not so strongly arcuate. Found among fresh water algae, Cape Van Beneden, Banco Land. It is rather difficult to point out satisfactory differences between this species and major. The pharynx of gerlachei is relatively smaller and is thicker walled, and its dorsal tooth is slightly farther forward. The number of labial papillae sixteen appears to be the same in each. The amphids are perhaps slightly farther back in major than in gerlachei. The number of papillae noted on the tail of the male of major is greater than that noted on the tail of gerlachei, but so far as the distribution of the dorsal papillae on the tail of gerlachei is concerned, they appear to accord very closely with those of major. The two species appear to be closely related. Fig. 26 on the previous page (after de Man). 13. M. fovearum (Dujardin) Bastian. This is an insufficiently known species and may have to be declared nomen nudum. Head a trifle angular. Pharynx angular, "armed with 2 to 3 straight pieces, each ? ? is. ^50' 93. 2 5 , (?) with a pronounced tooth in front of the ? - ? ? 3. ? middle." Tail tapering at first but retaining the same diameter through its pos- terior half, and ending in a sort of spinneret (?). Eggs in single series. Found at Rennes, France, in a fresh water ditch, along with Branchipus, ento- mostrica, Eitglena etc. De Man suggests that this species is related to tridentatus. 14. M. megalairnus, n. sp. Labial papillae obscure. Amphids obscure, half way between the apex of the dorsal tooth and the anterior extremity. Cardia large and 2.9 9. 28,. 's:?' 38 86. conspicuous, more or 1 - 8 2 - 6 3- 1 3 - 5 I- 7 ' less cylindroid, three- fourths as wide as the body. Intestine about 12 cells in girth, more or less distinctly tessellated. At the end of the anterior third the tail is one-fourth as wide as at the anus. Spinneret slightly swollen, with 2 very small digi- tate setae. About the roots of plants, in a tamarack swamp, Wisconsin, \J. S. A. This mononch is peculiar in the relatively meager development of the labial papillae and the pharyngeal teeth, and the weakness of the pharyngeal muscles. Flemming solu- tion to glycerine. Fig. 27. 15. M. macrostoma Bastian. Inner set of labial papillae inconspicuous; outer set fairly well developed. The neck tapers but little. The head, however, is rather markedly convex-conoid. De Man describes and figures 2 exceedingly minute submedian teeth at the base of the pharynx. CEsophageal lining strongly devel- oped. Intestine 12 to 15 cells in girth, tessellated. Posterior half or two-thirds of the tail of the female of practically uniform diameter, tapering but very slightly. Spicula arcuate, very slender, about twice as long as the anal body-diameter. Their proximal ends are not cephalated. They are accompanied by 2 accessory pieces, hardly one-third as long, arranged parallel to their distal parts. Supplementary organs, about 20, in the form of innervated papillae, spread over a distance nearly SUBGENUS MONONCHUS (S. s.461) 159 equal to the length of the tail, the posterior member of the series being a short distance in front of the anus. There are 3 pairs of somewhat equidistant subven- tral post-anal papillae on the anterior part of the tail. There are also lateral papillae on the tail. This beautiful, ac- ^ ^ 6 *| '& *|^ 2- M ^-7^-7-^^ _ ^ tive, rather common 2 6 ? 25 M 92 species is found in ? ? ^ ? T~~^ ll8 BB the soils of meadows and marshes in many parts of Europe ; it is also aquatic. The writer has followed Dr. de Man's rehabilitation of Bastian's macrostoma. Corresponding females which the writer has found at the Arlington Farm, Virginia, U. S. A., indicate the presence of exceedingly fine transverse striae, and of in- conspicuous wings. Amphids obscure, just behind the lips, difficult to see except in dorso-ventral view. The oesophagus receives the basal fourth of the pharynx, and in this region is very slightly swollen. The writer failed to see the minute basal onchi mentioned by de Man. The thin-shelled eggs, which occur in the uteri one at a time, are about one and one-fourth times as long as the body is wide and about half as wide as long, and are apparently deposited before segmentation begins. The writer has no doubt this species is syngonic. A female which had yet to undergo the final moult contained an egg which had its shell completely formed, and was evidently in a state preparatory to segmentation. Flemming solution to glycerine. Fig. 28 (after de Man). According to Bastian -the following differences exist between macrostoma and truncatus; macrostoma is 50 per cent longer, and is relatively narrower in the ratio of 3.5 to 5.3. Macrostoma tapers less in the neck, and has papillae, while truncatus has none. While macrostoma is the larger, its pharynx is no longer ; the onchus is a little farther forward. The intestine in macrostoma is less distinctly tessellated. The posterior part of the oesophagus in macrostoma is figured as having an internal expansion. These characters seem to the writer sufficient to separate the two species. It is probable that papillae on the head of truncatus were overlooked by Bastian. This would have been easy, for instance, if the papillae on truncatus are similar to those on megalaimus. See figure 27. 16. M. obtusus, n. sp. Papillae setose. The adjacent figure (29) is after 2.4 > 25. ^50+^ 87. Biitschli, whose 275 ? 472 ? 3.3 1-7 " figures seem to represent a different species from that figured by de Man under the name macrostoma, notwithstanding the general resemblances. The proportions of the tail and of the spicula are different in the two forms; the dis- tribution of the papillae on the tail is also different, and, while the number and position of the pre-anal ventral supplementary organs are about the same, their form as shown by Biitschli is decidedly different from that shown by de Man. In addition, Biitschli's figure shows 3 pairs of pre-anal, ventrally submedian papillae coex- tensive with the ventral row. Biitschli's data may there- fore, the writer thinks, be taken as establishing this new species. Synonym, M. truncatus Bastian of Biitschli. Found in the River Main, Germany ; common in mud and in aquaria and among aquatic plants, in moving water not foul. See also fig. 15. 1(30 (S. S. 462) THE MONONCHS 17. M. tunbridgensis Bastian. The Tunbridge mononch is interesting histori- cally as well as intrinsically, for it was an examination of numerous specimens of this aquatic nema that marked the beginning of the classical researches of the 6.7 24. '52' 20 2.4 2.1 2.4 2.8 7.8 24. 3.6 23. 3.7 89. 2.3 - 90. 1.3 n 2. 3.5 ?.6 ?.7 1.7 well-known English nematologist, H. Charlton Bastian. The upper formula is the average of glycerine specimens from the Arlington Farm, Virginia, U. S. A., while the lower formula is the average of the writer's balsam specimens from Tunbridge Wells, Eng- land. As a rule the 4iead is rather suddenly contracted opposite the pharynx, and this is perhaps the best distinguishing mark of the species. Bastian, who had an abundance of specimens, emphasizes this character. The adjacent figures are those of Dr. de Man, and show the pharynx relatively a little narrower than is usual. The tails of the writer's Tunbridge Wells specimens accord rather with Bastian's figure than with his description. As is often the case in other mononchs, the labial papillae stain more strongly with carmine than do adjacent tissues, so that the lip region as a whole appears strongly colored. Opposite the dorsal tooth there is an exceed- ingly minute, low, subventral projection. The form of the amphids is not fully determined ; they are located nearly opposite the base of the pharyngeal tooth, and have a width one-half to one-third as great as that of the pharyngeal cavity. Near the cardia the cesophageal lining occupies about one-fourth of the optical longitudi- nal section of the oesophagus. The intestine, which ma}' present a certain amount of tessellation, is about 10 to 12 cells in girth. The anterior two-fifths to one-half of the tail is conoid in such a fashion that at the middle the diameter is about one-sixth as great as at the anus. Thence onward the tail is nearly cylindrical, and ends in a very slightly expanded terminus armed with one or two very inconspicuous papillae. That a sticky substance often exists on the surface of the terminus of the tail is evident from the accumulation there of minute particles of foreign matter. Caudal glands appear to exist immediately behind the anus, but their nuclei have not been definitely made out as yet. The lateral fields appear to be one-third as wide as the body. Each ovary contains a score or more of developing ova, ar- ranged in several tiers in the distal half of the organ, but single file elsewhere. The somewhat elongated eggs are about one and one-third times as long as the body is wide, and about half as wide as long, and occur in the uteri one at a time. This seems to be primarily an aquatic species, though the writer has found it also in soil in the vicinity of rivers and streams. Fig. 30 (after de Man). 18. M. truncatus Bastian. CEsophagus conoid, its lining well developed. Intes- 2.5 ? 25. '50+* 86. tine about 12 cells ? if; sTa 3.4 ' 1 - 8 BB i n girth, more or ? 25. M 92.\ less distinctly tes- ? ? ? ? ' sellated. Lateral fields broad and distinct. It is a question whether to retain this species on the basis of Bastian's original description, or to accept Biitschli's description as a rehabilitation of Bastian's species. It is hardly likely that any species of Mononchus is destitute of labial papillae, and in this respect Bastian's description seems defective. The extreme reduction of the SUBGENUS MONONCHUS labial papillae so far recorded is shown in megalaimus. Biitschli and later authors describe and figure the papillae of truncatus as setose. It seems hardly likely that Bastian would have overlooked setose papillae such as those figured by Biitschli. In that case Bastian's truncatus should be retained as a species, probably having very inconspicuous labial papillae similar to those of megalaimus, while the data given by Biitschli may be taken as establishing a new species, for which the name obtusus is proposed. (See No. 16.) Found in a small pool, among decaying moss and liverwort, England. Fig. 31 (after Bastian). 19. M. dadayi Micoletzky. A striking character of this species, "M. macrostoma Bastian var. armatus Daday," as described by its author, is the presence of 6 small, ? ? 22. ? 86. tooth-like cuticular spines close H 1 ? ? ? 4~72 2.6 K6 '" around the mouth. No such structures have been seen in other species, and accordingly Micoletzky has proposed for the form the name dadayi. This is a littoral species. The description and drawings rest upon the examination of a single specimen. The original , m description is very brief and the accompanying illustrations, one of which is here reproduced, are meager sketches of the head and tail ends. A more complete examination of further 750 specimens is desirable. Fig. 32 (after Daday). 20. M. longicaudatus Cobb. Opposite the apex of the dorsal tooth there are refractive transverse thickenings of the wall of the pharynx in the ventrally sub- median region, and in front of these thickenings there are a few transverse striae. The lateral fields are two-fifths as wide as the body, and are distinctly to be seen, since they have definite lateral contours, doubtless owing to the thickness of the muscular layer. The lateral fields contain scattered, nearly colorless granules somewhat smaller than those contained in the intestinal cells. In young specimens the vagina is distinctly separated from the uterus by a deep constriction, and the uterus itself is bulbous near this constriction and narrower farther away. Longi- caudatus is a syn- 3. 6.? 26. ^55*23 88. gonic species. In 2~! 274 3~l 3~! 2.4 ' the adult and egg-producing specimens the eggs are seldom or never seen more than two at a time, one in each uterus. A predacious species, feeding upon other nematodes, upon rotifers and protozoa. It is cosmopolitan, and is found in rivers, ditches and pools, as well as in the soils of swamps and meadows. It occurs, sometimes in vast numbers, in the sand of the slow filter beds of the water-works of cities and towns. Flemming solution to glycerine. Fig. 33 ; also fig. 2, p. 132. Longicaudatus suffers from an internal disease caused by a fungus having a branched mycelium. The width of the mycelium is about half as great as the thickness of the body wall of the nema, and the septa oi the cells are separated from each other by a distance equal to the diameter of the body. There are two other diseases affecting this nema, one of microbe origin, the other of fungous origin; they appear, however, to be confined to the cuticle. One consists of short-styled, elongated-ellipsoidal elements on the surface of the body extending outward at right angles. These have been seen on the tail end. The microbe growth appears as a coating, sometimes of considerable thickness, and occurs on various parts of the body. It has been seen ff/OW . 464) THE MONONCHS at both extremities. The adjacent figure (34) depicts the tail end of a male found in Hawaii about the roots of sugar-cane. The general resemblance to the male as- signed by Biitschli to M. truncatus Bastian is very striking, yet the differences in detail are also pronounced. The number of supplementary organs is 16 instead of about 20, and the organs themselves relatively shorter and more plump. The spicula and their accessory pieces have the same general proportions and size. The tail also has the same form and proportions, but the termi- nal portion is more slender in the Hawaiian specimen, and the distribution of the papillae thereon is decidedly different, as will be seen by comparing figures 15 and 34. Male mononchs are so rare that the amount of variation that may exist in a given species is a nearly unknown quantity, so that it is not exactly easy to make intelligent comparisons between the males in these two cases. The Hawaiian male is supposed to be the male of M. longicaudatus, the only one that has ever been seen. It is interesting to note that when the spicula become long and slender the accessory pieces also become long and slender, but maintain their general form and are bifurcated at the distal end. Fig. 33 (on the previous page) and fig. 34. It is a curious fact that this, the only male of M. longicaudatus ever seen among the many thousands examined, should have come from soil, since longicaudatus is much less common in soil than in water. 2ia. M. dentatus, n. sp. This representative of a new subgenus is especially interesting as a guide to speculation concerning the relationship of Mononchus to 27. '62' 14 95. 1.1 mm 3.6 2.8 3.3 3.3 1.9 other genera. The scattered denticles are paralleled in certain marine nemas. The arcuate tail is conoid from the raised anus. The rather blunt terminus is about one- fourth as wide as the base of the tail. There is a pair of ventrally submedian, innervated papillae a little in front of the middle of the tail. The amphid is sometimes more elongated than shown in the illustrations. Description of a young female, from roots of orange trees, Bahia, Brazil. Fig. 35. For 21b, M. recessus, and 21c, M. decurrens, see Appendix, p. 184. 22. M. punctatus, n. sp. This species is proposed for the reception of the specimen described by Brakenhoff under the name M. papillatus Bastian, which appears to differ from 2.6 ? 25. 65' 26 93. any mononch hitherto ^2 ? ? 3~75 ? described in that the shells of the eggs are echinulate. It is placed in the subgenus Pri- onchulus, though with some doubt, principally because both the description and the figure of Brakenhoff show the pres- ence of denticles on the ven- tral rib of the pharynx. The author says: "Hier findet sich namlich cine, in der Mitte (und an den 2 Seiten) fein gezahnelte Leiste. Diese SUBGENUS PRIONCHULUS (S. S. 465) 163 Zahnelung erstreckt sich iiber eine etwa 0.016 mm. lange Strecke und beginnt distalwarts etwa in der Hohe der Spitze des dorsalen Zahns." The ellipsoidal eggs occur in the uteri one at a time, are about as long as the body is wide, and two-thirds as wide as long. Found among the roots of Alopecurus denticulatus , as well as aquatic habitats in the bottom of ditches and lakes in Germany. Fig. 36 and 36a (after Brakenhoff)' 23. M. muscorum (Dujardin) Bastian. The oldest, and one of the best known species. Intestine tessellated. Tail conoid and arcuate. The reflexed ovaries, each containing about a dozen ova arranged more or less in single file, extend half way fpl mrpt 2. 24. ;,32 2.5-3. 92. 1.9 rain 2.1 2.7 3.2 3.6 1.6 2. 3.2 3.7 4.4 2.5 back to the projecting vulva. The eggs are one and one-half times as long as the body is wide and three-fourths as wide as long. The anterior sexual organ is somewhat the larger. Fig. 37, left. This is a beautiful and rather common cosmopolitan species, occurring in swamps, marshes, meadows and moorlands. It has been found in various parts of Europe and is not uncommon in the United States. It was first found by DujardinWn the Jardin des Plantes, Paris, where it still thrives ; the writer recently found it about the roots of some heather imported thence. It feeds on smaller animal organisms, among them other nematodes. The following is a variety : M. muscorum (Dujardin) Bastian macrolaimus, n. var. Besides differing slightly in proportions from the type form of the species, the variety has a somewhat larger pharynx, with smaller denticles on the ventral rib. The submedian papillae of the outer sets are apparently double instead of triple, though at some distance behind the outer submedian papillae there is a special submedian innervation. Most of these minor differences are set forth in figures 36 and 37. Found in Cladonia rangiferina, tamarack swamp, Wisconsin, m U. S. A. Fig. 38, right. 24. M. longicollis, n. sp. A species resembling M. mus- corum, but which differs in the proportions of the various parts *"- and in the conformation of m ikl 3.1 10. 27. 93. the pharynx, the denticles 2.2 2.4 2.3 2.1 1.8 i> "" of which are irregular and inward pointing. Submedian papil- lae of the outer row double, instead of triple as in muscorum. Amphids relatively 154 (S- S. 466) THE MONONCHS ? 20. ? M ? - 3.6 an larger than in muscorum. Striae very difficult of resolution. Found about the roots of pitcher-plants and tamarack, in a swamp, Wisconsin, U. S. A. The differ- ence between this and muscorum may not be very important. Both are nema- tivorous. Flemming mixture to glycerine. Fig 39 (at bottom previous page). 25. M. spectabilis Ditlevsen. The muscular oesophagus encompasses the proxi- mal third of the pharynx, and has a conspicuous lining. The uteri may contain ? ? 20. '55' 96.8 , __ from 2 to 4 eggs, usually 2. The acute conical tail ? ? ? is strongly arcu- ate. The male is a little more slender than the female, and increases in size from a point where the supplementary organs commence, in such a way that the body assumes a maximum circumference near the anus. The copulatory muscles are strongly developed, and the num- erous, prominent, supplementary organs appear to have a subventral position, forming two longitudinal rows, between which is a groove. Fourteen of these supplementary organs are figured by Ditlevsen manifestly not the whole series. The arcuate spicula, which have a strengthening piece in their distal halves, are about one and one-half times as long as the anal body-diameter. Their proximal ends are not cephalated. At the widest part, toward the proximal end, they are about one-fifth to one-sixth as wide as the body ; thence toward the distal end they taper gently. The obscurely bifurcated accessory pieces, which in profile view appear to cross the spicula, are of the usual form, and are about one-third as long as the spicula, and about one-third to one-fourth as wide as long. Their distal extremities lie somewhat in front of the tips of the spicula and toward the ventral side of the body. The elongated eggs are nearly one and one- half times as long as the body is wide, and less than half as wide as long. Numerous specimens, the males as numerous as the females, found at Hellerup, near Oresund, Denmark. This species exhibits the phenomenon of flotation. Dit- levsen says : "If some material (meadow soil) is spread in a flat glass cup and water is poured over it, the mononchs will mount rapidly and be lying on the sur- face dry and shining." Fig. 40 (after Ditlevsen). 26. M. index Cobb. No striae seen. The .neck diminishes opposite the base of the pharynx to form a rather cylindrical, truncated head which is slightly expanded at the lip region. Amphids, one-fifth as wide 2.1 8.8 30. *69 15 95. 6 N as the head, are indicated by transverse mark- 2.4 3.2 3.5 3.6 2. ings, bent backward at each end, and located opposite the middle of the dorsal tooth. Denticles in about five rows, the outer rows more distinct. Pharynx half as wide as the head, and about three times as deep as wide. CEsophagus more or less conoid, with a massive lining occupying about one fourth of the optical sec- tion. Cardia pointed. Intestine few cells in girth; rather obscurely tessellated. Rectum half as long as the anal body-diameter. Longitudinal fields are visible throughout most of the length, and are about two-fifths as wide as the body. The diameter of the body increases somewhat just in front of the anus, and then dimin- ishes suddenly at the anus, so that the beginning of the tail is very considerably less in diameter than the portion of the body immediately in front of the anus. SUBGENUS MYLONCHULUS (S.s.467) The diameter of the cylindrical portion of the tail is about one-fourth that of the body at the anus. Caudal glands 3, egg-shaped, opposite the anus. Spinneret slightly apiculate and apparently unarmed. The eggs are evidently of large size. A single egg, not yet passed on to the uterus, was four-fifths to five-sixths as wide as the body, and about three times as long as wide. Common about the roots of sugar cane on various plantations on the island of Hawaii. Flemming solution to glycerine. 27. M. reversus, n. sp. This very interesting abnormal form possesses striae that appear resolvable into rows of dots. Intestine about 6 cells in girth, faintly tessellated. Tail more or 2 94 26 40' 1? 96 less cylindroid in the pos- 2.2 2.3 27? 74 2. ** l>1 n terior half, its terminus one-fourth to one-fifth as wide as its base. Lateral fields two-fifths as wide as the body. The eggs are of relatively large size, since an ovum not yet passed on to the uterus is 5 to 6 times as long as the body is wide. It is therefore likely that the eggs occur in the uterus only one at a time. The relatively broad ovary tapers but little; it contains about a dozen developing ova. Rio Janiero, Brazil, about the roots of Platonia insignis Mart. In general this species resembles incurvus and minor, but is readily distinguishable by the form of the sexual organ, and by the sparseness of the pharyngeal denticles, only a few of which are to be seen. When the female sexual organs reduce to one, this remain- ing one usually extends forward from the vulva. Here the reverse is the case; hence the specific name. Flemming solution to glycerine. Fig. 41. 28. M. obtusicaudatus Daday. Tail conoid, slightly arcuate; toward the end rather suddenly di- #- ------ ........ -~-V\ /N ^ 7 M- _ 1?Z!_JL1^ 1<9 M minished in size. The spinneret well marked. Found at Berlinhaven, Island of Salao, New Guinea, in fresh water. It seems probable from Daday's description that there are 3 teeth in the pharynx, 1 dorsal and 2 smaller submedian ones just at the base of the rasps. Probably fhe junction between the posterior and anterior elements of the pharyngeal walls is unusually prominent ; this would account for the "bogige leiste" mentioned in the original description and shown in the original figure along the anterior margin of the rasp. Fig. 42 (after Daday). Assuming Daday's drawing to be more or less conventionalized, this species might be regarded as identical with minor. 29. M. brachyuris Biitschli. Amphids appear as transverse slits opposite the onchus. Lining of the oesophagus strongly developed. Cardia plainly to be seen. 28. '62 18 96. Intestine tessellated. 2.2 Rectum half as long 274 i79 371 379 2.2 as the anal body-diameter. Caudal glands more or less saccate, opposite the somewhat raised anus. Tail some- what arcuate. Spinneret pore a little to the dorsal side of the middle of the terminus. The vulva is a conspicuous feature, owing to the thickness of the walls of the vagina, which is one-half as long as the body-diameter. Series of 166 (S. S. 468) THE MONONCHS male supplementary organs, according to de Man, about 12, mammiform and appar- ently protrudable except the two anterior and the posterior, which are more or less rudimentary. Series about twice as long as the tail. A cosmopolitan species. In Florida, the writer found this species feeding on the larvae of Heterodera radicicola, an extremely serious root pest. Fig. 43, bottom p. 467. 30. M. denticulatus, n. sp. Onchus opposed by two small subventral onchi farther back, the left a little farther forward than the right Found in the Zambezi River, South Africa, among fresh water algae. The peculiar form of the head and pharynx, and the unusually large number of denticles are the promi- nent characters of this species. Only a single mutilated specimen has been seen by Dr. Micoletzky. As it is un- likely that the large number of denticles shown in the original figures can be due to moulting phenomena, it would seem that this form differs distinctly from all others. Fig. 44 (after Micoletzky). As neither Micoletzky's text nor figure suggests moulting, the numerous rows of den- ticles are assumed to be normal, sp. Each rasp consisting of but 2 rows of denticles. The 12. 32. 54 Y 94. 31. M. sparsus, n. tail diminishes suddenly in size 2.9 behind the elevated anus, and 3.4 4.3 4.2 3.8 2^7^ tapers somewhat in the posterior three-fourths. The terminus is about one-fourth as wide as the base of the tail. The cau- dal glands (?) lie opposite the rectum. Found in sphagnum from greenhouses, Department of Agricul- ture, Washington, D. C., U. S. A. Flemming solution to glycer- ine. Fig. 45. 32. M. micrurus, n. sp. This odd form appears to have no submedian onchi. Rasps of only about four rows of denticles. Amphids not seen. Lining of the esophagus well-developed, occupying three-fifths of the optical longitudinal section. 3. 12. 33. Y 98. Intestine about 5 cells in girth, 27? 37i 3.7 3. 2.2 not tessellated, or only faintly so. Tail very short and strongly arcuate or bent. Spinneret about one-fifth as wide as the base of the tail. Rectum some- what shorter than the anal body-diameter; longer than the tail. Caudal glands not clearly seen, probably opposite the rectum. Ampullae of the caudal glands not very strongly developed. Described from young specimens found about Litchi roots, Fukien, China. Resembles bremcaudatus. Characterized by the extremely small and very strongly arcuate tail. The spinneret is sometimes turned nearly at right angles to ^ the axis of the tail. Flemming solution to glycerine. , Fig. 46. 33- M. incurvus, n. sp. Striae resolvable with diffi- adsl culty and into rows of dots. Dorsal onchus opposed by 2 inconspic- 2 . 7.4 28. *63' 2 t 96.2 . uous, ventrally 2.1 2.5 2.9 3.2 2.f^ " msiln submedian onchi of smaller size opposite its base. The lining of the oesophagus is a prominent feature, strnurph occupying about two-thirds of the apparent width of the oesophagus. Intestine 12 to 15 cells in girth, not "^ tessellated, its granules numerous and fine. Caudal ^ glands 3, broadly saccate, opposite the anus, their ampullae long and filling the posterior part of the tail. XTSO SUBGENUS MYLONCHULUS (S. S. 469)] 57 There is a flattish cardia. Anus raised. Longitudinal fields two-fifths to one-third as wide as the body. From the more or less elevated vulva the vagina leads inward at right angles to the ventral surface one-third the distance across the body. The eggs are one and one-half times as long as the body is wide, and occur one at a time in each uterus. The ovaries contain about a dozen developing ova. Sandy soil in a cranberry bog, Arlington Farm, Virginia, U. S. A. Also on the margin of the spring that gives rise to Salt River, Jamaica. Flemming solution to glycerine. Fig. 47 (at bottom of previous page). 34. M. sigmaturus, n. sp. Two very inconspicuous submedian onchi are found opposite the base of the dorsal onchus, just at the base of the rasps. Intestine 10 cells in girth, comparatively distinctly tessellated. The rectum is about as long as the anal body-diam- 2.3 12. 30. >64' 14 96.3 eter, and is some- what sigmoid. ll2 """ 2.4 2 3s 2.4 The anus is very distinctly visible on account of its contour, and on account of the refractive nature of the lining of the rectum. What appears to be a renette pore exists immediately behind the nerve-ring. The distinct lateral fields are about one-fourth as wide as the body, and are characterized by the presence in them of scattered granules much smaller in size than those of the intestine. The posterior part of the tail is somewhat digitate, and the whole is slightly sigmoid. From the anus the tail tapers rapidly to near the middle, so that if the posterior half were lacking the tail would be rounded. The diameter of the tail at the middle is about one-third as great as at the base. From the middle onward the tail for a short distance is of uniform diameter, and then tapers rather rapidly in the posterior fourth to a rounded or subtruncated spinneret. Small, somewhat finger-shaped setae are found on the tail ; one dorsally sublateral pair, a trifle in front of the anus ; another dor- sally sublateral pair near the middle of the tail but located on the more bulky part ; finally, a third ventrally sublateral pair a little in front of the digitoid part of the tail. The caudal glands are opposite the rectum. The eggs are about two and one- half times as long as the body is wide. The tapering ovaries contain 10 to 12 developing ova, arranged irregularly. Found in various parts of the United States and Mexico. Resembles minor and brachyuris, from which it may be distinguished by the form and structure of the tail. Flemming solution to glycerine. Fig. 48. 35. M. subtenuis, n. sp. Wall and dorsal tooth of the pharynx rather strongly developed. When the lips are closed the pharynx is hardly half as wide as long. Dorsal tooth slightly arcuate, its point located close to the base of the lips. The 1.5 5.6 26. ^72' 22 97. x submedian teeth - 75 1>3 ; l. are easily con- -Mi 2 97. . fused with the He TTa TA 272 fTer denticles. Lining of the oesophagus well developed, occupying one-fourth of the longitudinal optical section. There is a small conoid cardia. Intestine probably about 6 cells in girth, not definitely tessellated. Anus raised and conspicuous, the anterior lip somewhat massive and overhanging. The arcuate, conoid tail ends in a spinneret one-fifth to one-sixth as wide as its base. The ovaries, of which the posterior is somewhat the smaller, appear to contain about a dozen ova. Inconspicuous papillae appear on the ventral side of the female near the vulva. Two were noted behind the vulva and one or more in 1.5 6.2 25. *" r/ * 168 (S-S.470) THE MONONCHS front of it. The tail of the male is somewhat like that of the female but dimin ishes very suddenly behind the anus. Five pairs of innervated papillae have been seen on the tail of the male, two of them, however, exceedingly inconspicuous and easily overlooked : Of the three more conspicuous, one ventrally submedian pair is located a short distance behind the anus ; a second dorsally sublateral pair occurs a little behind the middle of the tail, and a third subventral pair occurs a short distance in front of the spinneret. Of the two more inconspicuous pairs, one is nearer the spinneret than that just mentioned, and the other, lateral, and slightly behind the middle of the tail. The arcuate spicula are about one and one-fourth times as long as the anal body-diameter. At their widest part, near the middle, they are about one-fifth to one-sixth as wide as the corresponding part of the body and thence taper in both directions ; they are not cephalated. The distal ends are obscurely two-pronged. The obscurely bifurcated accessory pieces are of typical form and size, about one-third as long as the spicula and about one-fourth as wide as long. Fourteen rather closely approximated, equidistant supplementary organs occur in front of the anus, occupying a distance about three times as great as the length of the tail. Internally the organs seem to be short, broad tubes of slightly varying diameter ; these are probably slightly protrudable. The protrudable portion is not hispid as is the case in M. major; on the contrary, it appears to be smooth. The anterior one and the posterior three of these organs are not so well developed as the others, that near the anus being reduced to a mere innervation ; the distance between this latter and its nearest neighbor is about twice as great as between any other adjacent members of the series. These organs give to the ven- tral contour a crenate or serrate appearance. The anal muscles are prominently developed. The ejaculatory duct is often filled with elongated spermatozoa, some- what resembling those of Dorylaimus, and similar in form to those figured by Dr. de Man for M. gerlachei. Each one may be one-fourth as long as the body is wide, or thereabouts. There are two outstretched testes. The blind end of the anterior is about as far behind the base of the neck as the latter is behind the anter- ior extremity. The blind end of the posterior seems to lie about twice as far in front of the foremost supplementary organ as this latter is in front of the anus. The spicula have a median stiffening piece, and their proximal ends lie toward the dorsal side of the body. Found about the roots of plants on the Arlington Farm, Virginia, U. S. A. Re- sembles M. minor, but in the proportions of the pharynx there are notable differ- ences. The walls are here thicker; the amphids are larger and farther back; the lips and onchus are strongly developed, so that when the pharynx is closed the cavity appears smaller than in minor. Opposite the anterior supplementary organ there is a fibrous ring, probably nervous. A similar structure has been noted in other species. There probably exist at this point in the body special nerve com- missures. Flemming solution to glycerine. Fig. 49 (near bottom of previous page). 36. M. subsimilis, n. sp. Striae of the cuticle more or less easy of resolution. Lining of the resophagus strongly developed, 3. 10. 34. Y 96. occupying three-fifths of the 3.1 3.6 4. 3.8 2.6 ' m longitudinal optical section. Anus slightly elevated, especially the anterior lip. The scat- tered granules in the cells of the intestine are small, but varia- ble in size, and do not give rise to tessellation. The more or less arcuate tail is conoid to the blunt terminus, which is about one-fourth as wide as the base of the tail. A ventrally sublateral innervated papilla occurs on each side near the middle of the tail. There are no caudal glands. De- scription derived from a single young female. SUBGENUS MYLONCHULUS (S.S.471) 169 About the roots of banana plants imported from Paris, France. Resembles brachyuris and minor, but differs in having no spinneret. The dorsal onchus is set farther back in the pharynx than in either of those species, and there are no traces of submedian teeth. The rasps also are less strongly developed. Flemming solu- tion to glycerine. Fig. 50 (at bottom of previous page). 37. M. obliquus, n. sp. Two small, ventrally submedian onchi present, opposite the base of the dorsal onchus. (Esophagus at first a little swollen; its lining well developed, and occupy- 2.6 9. 31. ^63'^ 98. ing one-fourth of the 27i 374 374 471 2.4 1>4 M optical longitudinal section. Intestine about 8 cells in girth, as a rule not distinctly tessellated. The conoid tail is slightly arcuate, and obliquely truncate at the spinneret, which is about one-third as wide as the base of the tail. The three caudal glands are located opposite the rectum, which ends externally in a slightly elevated anus. The ampullae of the caudal glands are well developed, and occupy the posterior two-thirds of the tail. Though the vuiva is more or less con- tinuous with the ventral surface, it is conspicuous on account of the refractive nature of the walls of the vagina. The elongated thick-shelled eggs are two and one-half times as long as the body is wide, and appear to be deposited before segmentation begins. The ovaries contain about a dozen developing ova, arranged partly single file, partly irregularly. A pair of ventrally submedian innervated papillae were noted near the middle of the tail of the female. From soil from Germany, along with specimens of Heterodera schachtii. Re- sembles brachyuris, from which it seems easily distinguishable by the large thick- shelled eggs. Flemming solution to glycerine. The habitat led to the suspicion that it was feeding on H. schachtii, but the writer was unable to establish the fact from the few specimens available for examination. Fig. 51. 38. M. lacustris Cobb. The amphids have the form of "slits," 3 to 4 times as long as wide, and are placed at the base of the lips nearly opposite the apex of the dorsal onchus. They 2.7 8. 28. *63* 96. /-^p^SscC H* are about one-sixth as 275 372 379 472 2.3 ' wide as the corresponding portion of the head. Intestine from 15 to 20 cells in girth, the cells closely packed with granules of variable size in such a manner as to give rise to a close and obscure tessellation. The well developed lateral fields are one-third as wide as the body. The anus is 'slightly raised. The lining of the rectum is distinctly refractive. The tail is ventrally arcuate, and ends in a blunt spinneret one-fourth as wide as its base, containing a well developed, internally ceratinized spinneret. The three caudal glands are arranged tandem in the anterior half of the tail, the foremost being opposite the rectum. The spinneret appears to have a needle-shaped valve. A pair of ventrally submedian innervated papillae has been noted a little in front of the spinneret on the female. The eggs, which appear to occur one at a time in the uteri, are about one and one-third times as long as the body is wide and four-fifths to five-sixths as wide as the body. Found in fresh water lakes, Michigan, U. S. A. ; about the roots of ferns, Panama Canal Zone ; and in the Silver Springs, Florida. Resembles M. brachyuris Biitschli, from which it differs in the form of the tail and spinneret. M. polonicus Stefanski seems to closely resemble this species. Sublimate to balsam. Fig. 52. 17Q(S.S.472) THE MONONCHS KM 39. M. polonicus Stefanski. Two minute teeth are found at the base of the buccal cavity. The conoid tail is somewhat arcuate from the raised anus, and ends in a truncated spinneret one-fourth as wide as its base. The three caudal glands are located in a tandem series in the anterior third of the tail. Description derived from young specimens found in vegetable detritus in the Czarna River, Poland. Said by its author to resemble the next species, No. 40. 40. M. minor Cobb. There are 2 minute, submedian onchi, easily overlooked. Amphids, only one-sixth as wide as the corresponding portion of the head, are 2.3 7.5 26. eo*"> 96.7 present opposite the 274 275 27& 371 2~7T^ """ apex of the dorsal tooth, and consist of arcuate, refractive markings hav- ing their convex side toward the lips. They appear to be about one-fourth as wide as the corresponding por- tion of the head. There are excessively minute striae or dentations of the inner surface of the margins of the lips; these structures are so fine that they might easily escape observation much finer than tne rasp-like teeth of the pharynx. The lining of the oesophagus occupies nearly one-third of the optical longitudinal section. The cells of the intestine contain small, somewhat uniform. rather evenly distributed granules. The anus is slightly raised, the anterior lip being a little more pronounced than the posterior. The conoid tail is rather strongly arcuate, or even more or less bent near the middle. The comparatively well developed spinneret is one-third as wide as the base of the tail, and pos- sesses a valve similar to that found in Mononchulus. The caudal glands are located opposite to, or a little behind the rectum. The lateral fields are two- fifths as wide as the body. This is a cosmopolitan species, found in tropical and temperate regions. It closely resembles M. brachyuris of Biitschli, but is smaller and differs somewhat both in the structure of the tail and in that of the pharynx. Osmic acid to water. Fig. 53. 41. M. brevicaudatus, n. sp. Walls of the pharynx unusually thick. Two ex- ceedingly small, ventrally submedian onchi, opposite the middle of the dorsal onchus. 2.7 9.3 32. >69' 18 96. Lining of the cesoph- 2.2 2.7 3.1 3.4 2.2 l ' 5 Bl11 agus prominent, oc- cupying one-third of the optical section. Intestine 6 to 8 cells in girth, faintly tessellated. Contour of the tail like that of the head of a duck whose beak is very short; from the anus onward having roughly an equilateral contour. Spinneret more elaborate than usual. The ceratinized walls of the vagina are plainly visible. The elongated eggs are two to two and one-half times as long as the body is wide. The ovaries taper but little. About a dozen females have been examined. No males have been seen. Sperm has been seen at the flexure in the ovaries. The species is probably syngonic. Found about the roots of plants in a cranberry bog, New Jersey, U. S. A. Resembles micrurus and brachyuris in its general form, but differs in the details of the pharynx and in those of the tail. The species is nema- tivorous, and also feeds upon rotifers. Sublimate to balsam. Fig. 54, in which, as m many of the original illustrations used in this chapter, what at first sight appear to be merely lines used as shading, are in reality carefully charted striae or lamina- tions of the wall of the pharynx. SUB GEN US ANATONCHUS (S. s.473) 171 42. M. japonicus, n. sp. The head is not set off in any marked fashion. Am- phids present in the form of elliptical markings nearly opposite the apex of the single dorsal tooth ; the length of their long 2.1 e.9 30. >67* 98. axes, which are placed transversely on the 274 271 279 27? 2~* l ' 2 ma head, is probably about one-sixth as great as that of the diameter of the head. The capacious pharynx is somewhat deeper than the head is wide; the anterior portion has a diameter more than half as great as that of the corresponding portion of the head, while the posterior portion has a diameter about two-fifths as great as that of the base of the head. The single, highly refractive dorsal tooth has its apex somewhat in front of the middle of the pharynx. The rasps consist of 5 to 6 rows of teeth, forming a group whose width is about one-fifth as great as the depth of the pharynx. The wall of the pharynx is strongly developed, and is very finely transversely striated in the posterior part. The lining of the oesophagus is an exceedingly distinct feature throughout its length, and appears to occupy about one-fourth of the optical longitudinal section. There is a small cardia. Intestine, about 8 cells in girth, very obscurely tessellated. The short, blunt, arcuate conoid tail is truncated at the terminus, which has a diameter about one-fourth as great as that of the base. The lateral fields are about one-third as wide as the body, and are composed of 2 rows of cells containing relatively large nuclei. This species rather closely resembles a number of others, and it is by no means certain that it is not identical with some one of them, perhaps consituting a variety. Curiously enough, it was found in Mississippi Bay, Yokohama, Japan. Sublimate to balsam. 43. M. tridentatus de Man. At the base of the pharynx are 2 minute denticles. Amphids unknown. Pharynx more or less triquetrous, with three well developed, 2. 6.5 22. '62' 26 2.1 2. 2.6 6.5 3. 22. 3.1 3.2 mm 2.7 2.1 2.6 3. 3.1 2. double, longitudinal ribs reaching from end to end. (Esophagus at first slightly swollen. Intestine distinctly tessellated. The arcuate tail is conoid to the termi- nus, which is about one-sixth as wide as the base of the tail. Each of the slen- der, arcuate spicula is cephalated by contraction and is supplied throughout its length with a median stiffening piece, and is crossed near its distal extremity on the outside by one of the rather broad, two-pointed accessory pieces, which are one-half as long as the spic- ula. Supplementary organs 15 to 17, apparently conical, 2 to 3 times as far apart anteriorly as posteriorly, where they are nearly contiguous. The posterior member of the series, the whole of which is about one and one-half times as long as the tail, is somewhat smaller than the other members, and is located a short distance in front of the anus. On the tail itself are a number of papilhe, dorsal as well as ventral ; 2 pairs on the anterior half, ventral, and 2 pairs on the posterior half, dorsal. It remains uncertain whether there is a spinneret and caudal glands. This striking species seems to be widespread in Europe in moist soil, and i rath-er common. Fig. 55 (after de Man). j 72 < s - THE MONONCHS 44. M. gracilicaudatus n. sp. Intestine about 12 cells in girth. The anterior fifth of the tail is arcuate conoid in such fashion that at the beginning of the second fifth the diameter is about one-third to one- 1.4 4.8 z\. -M^ 8 65. fourth as great as at the anus. Thence on- FTs fTi fTa TTs i.e' D-l B ward the tail tapers very gradually through the middle third, the posterior portion being cylindroid and somewhat narrower than the spicula. These latter are uni- formly arcuate, and about one and one-fourth times as long as the anal body- diameter. At their widest part, toward the proximal end, they are about one- fifth as wide as the corresponding part of the body. They taper gently in each direction, and are not cephalated. The small accessory pieces are of typical form, only about one-fourth as long as the spicula. The series of 19 contiguous supple- mentary organs is twice as long as the spicula, or equals 3 body diameters. Anteri- orly the organs are somewhat larger and also somewhat farther apart. The conical exterior portion of each organ seems to be more or less protrudable. These organs X750 inn are similar in form to those of major, though they are not echinulate. The anal and post-anal muscles are strongly developed. The anal muscles are found through- out the bulkier portion of the tail. The protruding muscles of the spicula extend backward in the tail to near the point where the tail diminishes rapidly in diameter, and there join the ventral part of the caudal wall. The post-anal papillae are con- fined largely to the more massive anterior fifth of the tail. On each side there is a ventrally submedian row about as long as the spicula, consisting of 4 to 5 mem- bers. Coextensive with them is a ventral row of 3 to 4 papillae. A little distance behind these, Avhere the tail begins to be smaller, there are 2 dorsally submedian SUBGENUS ANATONCHUS (S.s.475) 173 innervated papillae of smaller size. The supplementary organs are plainly inner- vated and the nerves can be traced through the cuticle and through the body mus- culature, and seem to be connected with internal more or less ellipsoidal cells whose nature remains unknown. The spinneret is very inconspicuous. The nature of the caudal glands remains uncertain. Found in marshy ground, Arlington Farm, Virginia, U. S. A., about the roots of fmpatiens, in black, clayey soil, with mud. Resembles M. dolichurus to a certain extent. It is regrettable that only a few specimens have been available for exami- nation, as it is a species well adapted to throw light on various features of mon- onch anatomy. Fig. 56 (on the previous page). Examination of the pharyngeal muscles of this species leads to a partial under- standing of the mechanics of the lips. The muscles which move the lips are long and slender, and pass from the lips backward along the surface of the pharyngeal capsule. They join the body wall some distance behind the pharynx. There are 2 separate groups of muscles, extensors and flexors. Of the 6 extensors 2 are shown in the illustration ; these are furcated opposite the middle of the pharynx, one half of each going to the lateral lip; the other half to a submedian lip. The joined fulcra of the 6 lips form a framework encircling the head. The extensors pass outside this framework. The flexor muscles are less clearly shown, but are mani- festly better developed. A group of 3 is shown lying between the 2 extensors. They appear as faint bands outside the pharynx passing forward, and beyond doubt are attached to the lips inside the ring of fulcra. The musculature of the lips is shown in the illustration and is further explained on page 140 in connection with the general description of the head. 45. M. dolichurus Ditlevsen. Neck tapering but little. Pharynx probably prismatic, and in transverse section somewhat triangular. About 7 denticles about the base, or near the base, of the pharynx. The arcuate tail tapers to the terminus, which is about one-eighth as wide as the base. The author mentions * ' ? . 2.5 1.8 the presence of 3 or 4 inconspicu- ously developed lobes at the base of the oesophagus, and it would appear from his figures that a spin- neret and caudal glands are pres- ent, the latter forming a tandem series near the anus. Menzel finds in the pharynx of Swiss specimens ^ of this species 3 teeth of equal size ; that is to say, the ventrally sub- median teeth are equal in size to the dorsal tooth. His specimens are / 2 to 5}/2 mm. long, and this probably represents the adult size, a Found in moist soil and meadow land, Jutland; Switzerland. Fig. 57 (after Ditlevsen). Menzel shows the papillae as much less conspicu- ous, and without the spherical tips. The original material consisted of but a single immature female. 174 (S ' THE MONONCHS 46. M. digiturus Cobb. Amphids occur opposite the anterior part of the pharynx. What appears to be a renette pore occurs just behind the nerve- ring. The anal region 3.3 8 . 26. 70 12 92. is somewhat 1.4 in.. 3. 3.4 3.4 2.3 raised. Behind the anus the tail diminishes rapidly in diameter, so that at the end of the anterior fourth it is about three-fifths as wide as at the anus. Thence, for some distance it is cylindrical, but be- comes somewhat abruptly convex-conoid in the pos- terior fifth and ends in a rather narrow, inconspicu- ous .spinneret. The lining of the oesophagus is a con- spicuous feature. Intestine not tessellated. The longitudinal ribs of the inner wall of the pharynx are rather conspicuous features, and extend from end to end of the pharynx. Found about the roots of banana plants, Fiji. Fig. 58. . 47. M. trichurus, n. sp. This outstanding form has an oesophagus that is slightly swollen where it receives the pharynx. The lining of the oesophagus is 2.6 7. 21. '52 11 67. prominent, occupying 2.3 . 2.4 278 279 1.8 l " * three-fifths of the op- tical section. Longitudinal fields one-fourth as wide as the body. Characters well set forth in fig. 14, p. 146. Found about the roots of orange trees, Bahia, Brazil. Bears considerable resemblance to M. gymnolaimus. It ap- pears possible from these investigations that the tropical mononchs, when more fully known, will prove especially interesting. Nearly all the more striking species here re- corded are from the tropics. The warm soils of the tropical regions teem with nematodes, many of them no doubt, especialy adapted to the peculiar conditions found there. The predatory mononchs in such soils will naturally enough have responded in structure not only to the climatic con- ditions, but also to the form and habits of their quarry. Fig. 59 (just above). / i' : :$Viar "" 48. M. gymnolaimus Cobb. The more or less triquetrous pharynx is strongly three-ribbed. Cardia of such 2.6 6.8 24. '67 16 86. 2.S mm 2.2 2.3 2.7 2.5 1.6 a nature as to give rise to a double constriction in the cardiac region. In- testine about 12 cells in girth. What appears to be a renette pore occurs immediately behind the nerve-ring. The lateral fields are about one-fifth as wide as the bodv. The tail tapers regularly to near the terminus ; it is, however, cylindroid for a short distance in front of the spinneret. Vulva not prominent. The uterus is as long as the reflexed portion of the ovary, which SUB GENUS IOTONCHUS (S. S. 477) 175 reaches two-fifths the way. back to the vulva. The ova are for the most part arranged single file. This nemativorous species will probably prove cosmopolitan. About roots of banana, Fiji; of Platonia insignis, Rio Janeiro, Brazil; roots of various plants, Arlington Farm, Virginia, U. S. A. Fig. 60 (on the previous page). 49. M. consimilis, n. sp. Amphids, unlike those of gymnolaimus, apparently duplex, located a little behind the base of the lips ; one-fourth as wide as the cor- responding portion of the head. Wall of the pharynx strongly developed. Rather closely resem- 3.2 9.1 26. 68' 86. bles M. gymnolaimus, 2.4 2.7 2.7 2.4 2.1 1-1 M but has the walls of the pharynx much more strongly cer- atinized, and is of much smaller size. The pharynx is j~ela- tively SO per cent longer. The spinneret is not swollen as in gymnolaimus. Description and figures derived from a single, immature female specimen from about the roots of Platonia insignis Mart., Brazil. The figure of gymnolaimus shows, on the ventral side, near the front of the pharynx, an inward projection, probably representing the optical section of the junction of elements in the pharyngeal wall. No such appearance was observed in consimilis. Fig. 61. 50. M. rapax, n. sp. Intestine about 12 to 20 cells in girth, faintly tessellated. The female organs 'are probably double and symmetrical. The conoid tail tapers somewhat in front of the anus to a plain, symmetrical, unarmed spin- 2.5 6.5 21. 61. 90. , 27 272 276 271 fTT^* dl neret about one-sixth as wide as its base. One and one-half tail-lengths in front of the anus there is a con- striction in the intestine, which ap- pears to be due to the presence in that region of ' commissures, as if, possibly, nerves encircled the intes- tine at that part. Found about the roots of plants, Arlington Farm, Virginia, U. S. A. Nemativorous. Only young females have been seen. As its name, rapax, indicates, this species is a rapacious one, swallowing other nemas whole, even when half as long as itself. Fig. 62. 51. M. rex Cobb. This "king" of the mononchs has low, broad, inconspicuous labial papillae that do not interfere materially with the rounded contour of the front of the head. The lips are bulky and powerful. No amphids have been seen. The pharynx is armed with very powerful 2. 6. 20. 'se* 37 ei. muscles. The intestine is tessellated. The fTe UT 2~. ?72 lateral fields are one-fifth as wide as the 2 5>5 20> M 50 body. The conoid tail tapers more rapidly us F79 271 iTa t.5 ' - a - y - mB at first, being nearly cylindroid in the posterior two-thirds, where it is about one- eighth as wide as at the anus. The spinneret, which is slightly expanded, bears two ventrally submedian papillae, after the manner of longicaudatus , but slightly larger 1.4 86. THE MONONCHS in proportion. Three caudal glands are present. Each uterus is capable of carrying one and possibly two eggs at a time. These are about one and one-fourth times as long as the body is wide, and half as wide as long. The tail of the male tapers more rapidly at first than that of his mate. Supplementary organs 17, prominent, closely approximated, equidistant, occupying a space equal to one and one-half times the length of the tail. The spicula are about twice as long as the anal body- diameter. Found at depths of from about 200 to 1200 feet in Lakes Manapouri and Wak- atipu, New Zealand. 1.6 8. 17. <63' 26 9 3.5 m arcuate, duplex, longitudinal ribs strengthen the walls of the phar- ynx and reach from end to end, one being dorsal, the other two ventrally submedian. Amphids difficult to see. (Esophagus at first slightly expanded. The ces- ophageal lining is not so promi- nent as in many other species; its optical section finds expression in 3 or 4 parallel lines, occupying about one-fourth of the longitu- dinal optical section. There is an inconspicuous, flattish cardia. In- testine about 8 to 12 cells in girth, faintly tessellated. The tail is conoid to the plain, unarmed con- oid terminus. The base of the spinneret is about one-fifth as wide as the base of the tail. The clavate caudal glands form a close tandem in the anterior third of the tail. The anus has rather conspicuous, with well developed, though not protrud- ing lips. There is a pair of innervated lateral papillae near the middle of the tail of the female. Both in front of and behind the vulva, especially behind, there are inconspicuous papillae, occupying a distance equal to twice to thrice the length of the body-diameter. The two equal, arcuate, rather slender spicula are one and one-half times as long as the anal body-diameter, and are of nearly uniform size throughout the greater part of their length. However, beginning near the slightly truncated tips they taper slightly in the distal sixth. The proximal ends are also narrowed slightly and lie well toward the dorsal side of the body, at any rate when the body is incurved. The two accessory pieces, each about two-thirds as wide as the spicula, are located opposite the distal portions of these latter. When seen in profile they appear to lie nearly at right angles to the body axis, and seem to cross the distal parts of the spicula. They are about two to three times as long as wide, and their distal extremities are diminished and bifurcated, the two prongs of the fork forming a U-shaped figure. When at rest these accessory pieces, as usual, are well inside the anus, in fact appear as if lying immediately under the lateral fields. In front of the anus there is a uniform series of about 16 equidistant, closely approximated, innervated supplementary organs, occupying a distance about equal to the length of the tail. When the tail end of the body is incurved, each organ appears on the ventral contour as a flattish cone, at the apex of which is a nerve ending, which from this point extends inward and forward. Brown, sandy soil, Arlington Farm, Virginia, U. S. A. This nemativorous 'mon- onch is distinguished from all others by the relative broadness of the pharynx, and by the position and size of the basal onchi. Especially well adapted to show the structure of the lip muscles and other organs of the head. Fig. 67. SOIL FERTILITY (s. s. 481) 170 57- M. acutus, n. sp. CEsophagus bulbous at first, the swelling being prolate. Intestine about 10 cells in girth. The arcuate conoid tail is practically acute. There is a pair of 2.6 sublateral, 2.7 7.5 23. 94. 8.1 Hi. 3.2 3.3 3.4 innervated papillae near the beginning of the pos- terior third of the tail. Anus not raised. Fig. 68. Found about the roots of rhubarb in loose, brown, sandy soil, Arlington Farm, Virginia, U. S. A. Nemativorous. One specimen was ob- served which had swallowed another mononch. This is one of the most instructive forms. It is desirable that the more minute structural details of nemas be very carefully investigated with a view to increasing our knowledge of their comparative anatomy. The different parts of the digestive or- gans of nemas, small as they are, are as pro- foundly modified in harmony with the nature of the food as those of higher animals. The digestion of starch requires a different organic mechanism from that for digesting meat. The nemas have specialized to a high degree in the matter of food, and their digestive organs are correspondingly diversified. NEMAS AND SOIL FERTILITY No one with a grain of imagination can engage in such studies as the foregoing without sooner or later asking himself questions of a general nature concerning the biology of the soil, for he gradually comes to sec how almost infinitely numerous and varied are the organisms inhabiting it; a population in which the nemas are but an element. The answers to these questions will lead to a new view of soil fertility. The revolution wrought by Liebig's ideas concerning the chemistry of the soil spent itself only to show us that, grand as it was, it was little more than an overture. Subtler forces and more intricate relationships than any indicated in these earlier conceptions must be considered. We now see, or are beginning to see, that the value of manure and of the ro- tation of crops is to be explained not simply on the basis of the exhaus- tion of certain elements in the soil, but also, and probably in some in- stances mainly, on the basis of an opposite process, an accumulation of certain organisms and substances in the soil. Who knows but that the existence of annuals may be due in some measure to this latter fact? May not these elaborate provisions for the distribution of the seeds of annuals be in some measure a means of escaping these accumulated hostile forces in the soil ? After all the word Agriculture is more or less of a misnomer. We cultivate, not so much the field, as plants. What we are really after is sunshine, for we are lost unless we can convert our infinitesimal part of the energy of this nearest star into food, clothing and shelter. This we do by utilizing the life forces of certain plants and animals, and these are not so few as we dreamed in our older philosophy, for none of our "domesticated organisms" can any longer be considered by itself. Every lgQ(S.S.482) THE MONONCHS such organism is reared in the midst of a host of other organisms, visible and invisible, and often it is these others that determine agricultural suc- cess or failure. The soil is the habitation of a vast community of beings with all the attributes of other huge agglomerations of living things having varying needs, instincts and aspirations; and it is just as inappropriate to look upon it as inorganic as it would be to look upon a great city as merely an agglomeration of hills, streets and houses. Here in the soil are beings in enormous variety; multiplying, growing, dying; competing, fighting, co- operating one with another, with an activity almost if not quite defying the imagination, and we need what may be called soil biologists or geo- biologists, who shall understand, as far as possible, this interplay of life forces that gives us food, fiber and fuel. To a considerable degree our progress in agricultural knowledge in the not distant future will be in pro- portion to the firmness with which we lay hold of and act on this idea. SUMMARY 1. The genus Mononchus is composed of scores, possibly hundreds, of species, divisible into distinct subgenera. The number of known species is hereby more than doubled. 2. The genus is of world-wide distribution, and many of the species are cosmopolitan. Mononchs occur in all kinds of arable soil, sometimes in hundreds of millions per acre. 3. Most mononchs, probably all, are strictly carnivorous. They feed on a variety of living microzoa, prominent among which are other nemas. 4. Injurious nemas are devoured by mononchs, and it is desirable that this trait of mononchs be carefully investigated with a view to utilizing it, if possible, in diminishing the enormous crop losses due to plant infesting nemas losses amounting to many millions of dollars annually. 5. The lips are moved by long muscles, connecting proximally with the body wall behind the pharynx. These muscles lie along the outer surface of the pharyngeal capsule and act in such a way as to pull the lips inward and outward radially about a series of fulcra existing in a framework encircling the head along the margin of the pharynx. The lips are the mechanical complements of the dorsal tooth and denticles. While most mononchs bolt their food, some give it a certain degree of mastication. The appetite is sometimes voracious. 6. Many mononchs, probably most, are hermaphroditic, even to the degree of syngonism. In the typical case investigated the minute sperm cells of female origin are functional. 7. Well developed glands, salivary in character, occur in the mon- onch oesophagus, and empty duectly into its lumen, and both indirectly and directly into the mouth cavity. BIBLIOGRAPHY (S. s. 483) jgl 8. What appears to be an excretory pore of the usual type seems universal near the nerve ring. 9. The outer labial papillae are the homologues of the ordinary cepha- lic setae of other nemas, and are therefore most probably tactile in func- tion. This leaves it probable that the inner papillae are devoted to the senses of taste and smell. 10. Amphids are always present in the form of small lateral more or less elliptical structures near the lips, and are connected with internal elements extending inward and backward. 11. A functional spinneret is present in a majority of the species. 12. The cuticle is always finely transversely striated. 13. Mononchs probably moult four times. 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(25) DE MAN, J. G. 1906. Nematodes de 1'Ile de Walcheren. In Ann. Soc. Roy. Zool. Mala- col. Belg., p. 156-174, 17 fig. (26) DE MAN, J. G. 1907. Nematodes libres de la Seine. In Ann. Biol. Lacustre, t. 2, p. 9-29, 3 pi. (27) DE MAN, J. G. 1912. Helminthologische Beitrage. In Zool. Jahrb., Sup. 15, Bd. 1, p. 439-464, 2 pi. (28) DlTLEVSEN, H. 1911. Danish free-living nematodes. In Vidensk. Meddel. Naturhist. Forening, Bd. 63, Heft 1, p. 213-256, 5 pi. (29) DUJARDIN, F. 1845. Histoire Naturelle des Helminthes. 654 p., 12 pi. Paris. (30) HOFMANNER, B. 1913. Freilebenden Nematoden. In Zool Anz., Bd. 42, p. 413-418, 4 fig. (31) HOFMANNER, B. 1913. Nematodes libres du Lac Leman. In Rev. Suisse Zool., t. 21, no. 16, p. 589-658, 2 pi. BIBLIOGRAPHY (S. s. 485) jg3 (32) HOFMANNER, B., and MENZEL, R. 1915. Freilenbenden Nematoden aus der Schweiz. In Rev Suisse Zool t. 23, p. 109-243, 3 pi. (33) JAGERSKIOLD, L. A. 1909. Freilenbende Siisswassernematoden. In Siisswasserfauna Deut- schlands, (Brauer), Jena, Heft IS, p. 1-46, 65 fig. (34) KLAUSENER, C. 1908. Fauna eines hochgelegen Alpensees. In Internat Rev Hydrobiol Bd. 1, p. 142-152, 1 pi. (35) MARCINOWSKI, KATI. 1909. Parasitisch Nematoden. In Arb. K. Biol Anst. Land u Forstw Bd. 7, Heft 1, p. 1-192, 1 pi., 76 fig. (36) MENZEL, R. 1912. Freilebande Nematoden, Umgebung von Triest In Rev Suisse Zool., t. 20, p. 536-542, 2 fig. . (37) MENZEL, R. 1913. Mononchus sschokkei n. sp. In Zool. Anz., Bd. 42, p. 408-413 4 fig. (38) MFNZEL, R. 1914. Mikroskopische Landfauna der Schweiz Hochalpen. In Arch. Naturgesch., Abt. A, Heft 3, p. 1-98, 1 pi., 16 fig. (39) MICOLETZKY, H. 1912. Fauna einiger Seen Salzburgs. In Zool Jahrb., Abt. System., Geogr. u. Biol. Thiere, Bd. 33, p. 421-444. (40) MICOLETZKY, H. 1913. Nematoden der Ostalpen. In Sitzber. K. Akad. Wiss. (Vienna), Math. Naturw. Kl., Bd. 122, Heft 4, p. 543-548. (41) MICOLETZKY, H. 1914 Nematoden der Ostalpen. In Zool. Jahrb., Abt. System., Geogr. u. Biol. Thiere, Bd. 36, p. 331-546, 10 pi., 1 fig. (42) MICOLETZKY, H. 1915. Fresh-water nematodes of South Africa. In Ergeb. Bot. Forsch. Reise Deut. Ostafrika. (43) OERLEY, L. 1880. Monographic der Anguilluliden. In Termeszet. Fiizetek, Bd. 4, Heft 1-2, p. 1-165, 7 pi. (44) PLOTNIKOFF, B. 1901. Nematoda, Oligochaeta, und Hirudinea. In Ber. Biol. Siisswasser- Stat. K. Naturf. Gesell., St. Petersburg, Bd. 1, p. 244-251, 2 fig. (45) STEFANSKI, W. 1914. Nematodes du Bassin du Leman. These de 1'Universite de Geneve. (46) STEFANSKI, W. 1915. Nematodes de Pologne. In Zool. Anz., Bd. 45, p. 346-349, 6 fig. (47) STEINER, G. 1913. Freilebenden Nematoden aus der Schweiz. In Arch. Hydrobiol. Planktonk, Bd. 9, p. 259-276, 29 'fig. (48) STEINER, G. 1916. Freilebenden Nematoden. In Zool. Anz., Bd. 46, p. 336-368, 11 fig. (49) STEINER, G. 1916. Freilebenden Nematoden von Nowaja-Semlja. /Zool. Anz., Bd. 47. (50) ZSCHOKKE, F. 1900. Die Tierwelt der Hochgebirgsseen. In Nouveau Mem. Soc. Hel- vetique Sci. Nat., t. 37, p. 1-400, 8 pi. (S. S. 486) THE MONONCHS APPENDIX r^ oox ^ U> t 7> " 14 > ^ : F 8 p"^-- ^^-v-f'M $$ .! ! j" #? >5!r/?er oe lit w tic OP im an spn The above diagram illustrates the decimal formula used herein. 6, 7, 8, 10, 6 are the transverse measurements, while 7, 14, 28, 50, 88 are the corresponding longitudi- nal measurements. The formula in this case is : - 14- 28 ' 50- 88- . The unit of 6. 7. 8. 10. 6. measurement is the hundredth part of the length of the body, whatever that may be. The measurements become, therefore, percentages of the length. The absolute length is given in millimeters as a final non-paired term. The measurements are taken with the nema viewed in profile ; the first are taken at the base of the pharynx, the second at the nerve-ring, the third at the cardiac collum or end of the neck, the fourth at the vulva in females and at the middle (M) in males, the fifth at the anus. Fig. 68. M. recessus, n. sp. No. 21-b. Striae excessively fine. Lips with 14 papillae. Intestine about 5 cells in girth, 2.8 6.9 30. '63 12 91.5 faintly tessellated. Cau- 2^ 27i 27? 274 TF^ dal glands small and inconspicuous. Tail tapering rapidly on the ventral side behind the anus ; thence onward arcuate and conoid, with spinneret. Habitat: soil of a tomato field, Naranjo, Fla. This species, together with decurrens and dentatus, constitute the new sub-genus Sporonchulus; it is interesting to note that so far as known all of them are tropical and below the x 750 ^ m ^ i" average size. Fig. 69. M. decurrens, n. sp. No. 21-c. Striae excessively fine. Intestine 7 to 8 cells in girth, the cells packed with granules, which, however 2.9 9. 24. Y 95.9 do not give rise to a tessel- 2 - 9 4. 4.2 4.6 2. lated appearance. Tail arcuate conoid, tapering from in front of the anus. No spinneret, or doubtful ; no caudal glands. Ex- cretory pore (?) just behind the nerve ring. Anus more or less elevated. Habitat : Plant Introduction Gardens, Miami, Fla. 53-b. M. fasciatus, n. sp. Like M. bathybius, No. 53. Characterized by large, powerful lips, set off by a deep constriction, in 2.4 5.6 16. '64'=" 90. ^ ^ ^ the depths of which is a double refractive line. 2.3 2.3 2.4 2.4 1.8 Teeth 3, small, equal, sub-basal ; tail conoid, no spinneret. Papillae 14. Habitat : About roots of camphor, Florida. Nemativorous. Erratum. After Soil Science went to press it was found that similis and tenuis are invalid as designations of new mononchs, owing to Mononchus similis Cobb 1893, and Mononchus tenuis Daday 1908, the latter not a mononch. The present M. similis is therefore hereby changed to M. subsimilis, and M. tenuis to M. sub tenuis. The ref- erence to M. megalaimus in "Nematodes mostly Australian and Fijian," Cobb, is a misprint for M. gymnolaimus. The overlooked M. similis is as follows : 53C. M. similis Cobb. 3.3 8. 24. u '58' u 86. Pharynx three-fifths as wide as the head, two- 3. sTs 471 4~5 2A 1-8 mni thirds as wide as long ; tessellated intestine fifteen cells in girth ; anus conspicuous, depressed ; spinneret one-eighth as wide as the base of the tail. Clarence River, Australia. Habitat : About roots of cane, Harwood, MONONCHUS SUBGENERA MYLONCHULUS PRIONCHULUS longicollis GENUS MONONCHUS IOTONCHUS consunilis bathybius fff flrf SUBGENERA SPORONCHULUS ANATONCHUS acutus FILTER-BED NEMAS: NEMATODES OF THE SLOW SAND FILTER-BEDS OF AMERICAN CITIES (Including new genera and species) WITH NOTES ON HERMAPHRODITISM AND PARTHENOGENESIS* CONTRIBUTIONS TO A SCIENCE OF NEMATOLOGY, VII BY N. A. COBB United States Department of Agriculture The nemas here described were collected from the filter-beds of several American cities, incident to a rather extensive investigation of nemas of economic interest. A study of them has afforded me such an interesting and suggestive glimpse of the biological conditions in slow sand filter-beds that I venture to think an account of it may be of some slight use to sanitarians, and to engineers connected with city and town water works. The biological observations, more particu- larly those on the vanishing series of spermatozoa in syngones, may prove of interest to zoologists and geneticists. NATURE AND NUMBER OF THE ORGANISMS FOUND Few Green Organisms. Comparatively few green organisms occur in covered slow sand filter-beds, especially if the water passes through a subsidence reservoir before entering the beds. Practically all the living forms found are colorless or nearly so, and most of the larger ones are animal. To me the most striking organisms in every sample of sand examined were the nemas. Period of Use. Renewal. From time to time a few inches of the topmost sand of slow filter-beds is renewed; the old sand is removed and fresh sand spread in its place. The period of use, the time between any two successive renewals, varies from a few weeks to a few months, according to the practice of the engineer in charge. Toward the end of a period of use the number of nemas in the topmost three inches of a bed often mounts to hundreds of millions per acre, and sometimes exceeds a thousand millions per acre. At this latter figure each glass of drinking water must percolate through sand containing at least about a thousand nemas. Dozens of Species Found. Often the nema population is of a mixed character, but sometimes it is comparatively homogeneous. On *Waverly Press, Baltimore, Jan. 11, 1918. 190 FILTER-BED NEMAS one occasion, at the end of a period of use, I found ninety-six per cent of the nemas to consist of but a single species. About thirty species were found inhabiting the various beds examined, twenty-five species being found to inhabit the beds of one city. My observations make no pretence of being exhaustive, and I presume further research may easily double these numbers. Most of the species are of only occasional . occurrence ; those figuring prominently in the activities of the beds are only about half a dozen in number, and of these not all are equally important. THE MORE COMMON SPECIES Commonest Species Carnivorous. Of the four more important species, (1) Mononchus longicaudatus, (2) Ironus ignavus, (3) Tripyla monohystera and in a lesser degree (4) Ironus longicaudatus, I have shown that all are carnivorous, that they feed upon a variety of living organisms, and that no one of them confines itself to a single kind of food. Mon- onchus longicaudatus, for instance, feeds upon several species of nemas, upon rotifers, and upon a variety of protozoa. The same is true of Tripyla monhystera. In the struggle among these filter-bed organisms it appears that sometimes one species may almost annihilate others. This accounts for such cases as that in which Mononchus longicaudatus constituted ninety-six per cent of the nema population of a bed. ROTATION OF THE FLORA AND FAUNA Seasonal Fluctuations. I know little about the seasonal fluctuations ; merely that they exist and that sometimes they are very marked. For instance, on January 6 samples of sand were gathered from various locations on a Washington filter-bed. This bed had been in operation about six months, a period longer than in the case of any previous examination (summer collections). About the same range of species was found in this sand as had been found in all previous experience taken together, but the smaller nemas, including Monhystera, were much more abundant in this than in previous collections, and seemed to be thriving. A large Dorylaimus that had been extremely rare in previous collections was fairly common in this January collec- tion. Achromadora minima was also more common. Finally there were one or two small species not hitherto found, Cylindrolaimus ob- tusus and a Rhabdolaimus. Whether these faunal differences were due to the winter season or to the long time the bed had been in use remains in certain instances undetermined, very likely some of them were due to both causes. Economic Bearings. Apart from seasonal fluctuations, there is a rotation in the fauna and flora incidental to the management of the FILTER-BED NEMAS AND PUBLIC HEALTH 191 beds. Beginning with a new period of use, it appears that minute species, e.g., bacteria and protozoa, having a short life cycle and suited to the new conditions, first make their appearance; these multiply and become the food of succeeding species, which in their turn give place to others. The problems presented are of great biological interest, and may not be without some bearing on public health. Beyond doubt they have a more or less important relation to the economical and effective management of the filter-beds. DETERMINING FACTORS OF FILTER-BED POPULATION Organisms other than Nemas. Many other kinds of organisms are found in filter-beds, some of them in far greater numbers than the nemas. Bacteria, fungi and protozoa occur, of course, in abundance, and are, I believe, the organic basis on which is built up the later animal pop- ulation consisting of organisms of larger size, such as the nemas. Rotifers are not uncommon. Small oligochaetes, earthworms, occur, especially after long use, but never in such myriads as in sewage. Small crustaceans, such as daphnia and cy clops, sometimes occur, but I have never seen them in large numbers. Occasionally aquatic insects are found. The filter-beds of each city present biological peculiarities dependent upon the source of the water supply, for the biological characteristics of filter-beds depend to a considerable extent on the climatic and geological conditions prevalent on the water-shed from which the supply is drawn. PHYSIOLOGICAL SIGNIFICANCE OF FILTER-BED NEMAS Illness from Change of Water. It is a well-accepted idea among physicians, as well as laymen, that a change of drinking-water may cause intestinal disorders; why they are thus caused is not always clear. If the waters in question are widely different in composition, for instance one soft and the other hard, it is easy to understand how intestinal derangements might follow a change from one to the other; but are the derangements due to change of water always associated with such marked chemical differences? Do not intestinal disturbances follow changes of water in which the usual tests would show but very slight differences? Soluble Excreta in Drinking-water. Is it possible that slight quantities of organic substances found in drinking water and of a character as yet unknown, might, under some circumstances, exert a powerful physiological influence? If this question be answered affirmatively, a wide field of investigation is opened up in connection with potable waters, and it is in this connection that the present researches are 192 FILTER-BED NEMAS definitely suggestive. The filter-beds, after they have been cleaned and again put to use, soon become the habitat of a succession of various organisms, animal as well as vegetable, so that at the end of a period of use it is no exaggeration to say that the sand through which the water percolates swarms with them. To state a definite case quantitatively, it has been shown during these examinations that such filter-bed sand may contain hundreds of millions of nemas per acre in the top three 1 inches. Each of these nemas is excreting material of which the soluble portions must pass into the city's water supply, and if in the course of its passage through the filters, flumes, and delivery pipes this soluble matter is not precipitated or otherwise altered, it is present in every glass of drinking-water. FLAVOR OF DRINKING WATERS Drinking-water Connoisseurs? The excreta of any given filter-bed organism must be different from that of any other, and though the differences may be slight between similar organisms, there are good reasons for thinking that the differences among the organisms of the filter-beds of different cities are great enough to cause material dif- ferences in the nature of their excreta. Such soluble parts of the excreta as pass into the drinking-water must play a role in imparting to the water its flavor and other qualities. This is enough to make one wish that we had connoisseurs to assist us in the selection and control of drinking-water, as we have connoisseurs in wine and tea, connoisseurs or experts capable of distinguishing minute differences in the flavor of drinking-waters. At first thought this may seem too fine-spun, and yet when we think of the care exercised in selecting wines, teas, and other beverages, and compare their actual importance with that of drinking- water, it may not be going too far to suggest that consideration be given to the possibility of determining th qualities of drinking-water by flavor and other tests in addition to those now in use. I think experienced persons with a delicate sense of taste will bear out the statement that the drinking-water of each city has its characteristic flavor. If half a dozen glasses of fresh drinking-water could be assem- bled from the water supplies of as many cities, I have little doubt that a person with a delicate sense of taste w r ould be able to tell one from another blindfolded, at any rate where the differences were most pronounced. In this discussion it matters little that the amount of the dissolved substances thus suggested as a possible cause of differences in the physi- ological action of drinking-water is minute, for it is a well-established fact that very minute quantities of various substances may have a pro- CONTROL OF FILTER-BED NEMAS 193 found effect upon the human organism. Such reflections lead to the sug- gestion that the study of filter-bed organisms is one that should be prosecuted more vigorously. We have developed a few excellent chemical tests, and, so far as it goes, an excellent system for determining the bacterial content of drinking-water. Why not go a step farther and make at least an attempt to determine the nature of the minute quan- tities of soluble organic substances of physiological significance which may be present, and the origin and nature of these substances. POSSIBLE CONTROL OF FILTER-BED ORGANISMS If it should be found that the presence of a particular micro-organism in filter-beds is deleterious, is it possible so to manage the beds as to exclude the micro-organism, or counteract its effect? Already I feel sufficiently conversant with some of the facts to predict that such control will prove feasible, at least in some instances. In the case of Mononchus longicaudatus for instance, as soon as we know the natural distribution of the Mononchus; its relationship to the seasons of the year, if it has any significant relationship of that kind; the period of its life cycle; its rate and method of reproduction; its food; its enemies; then, almost beyond doubt we shall be able to suggest means for its control. So with other organisms. To secure a reliable filter-bed census it is necessary to examine the sand as soon as collected. After a short period under laboratory con- ditions the population begins to change: e.g., sand which at the time it was removed from the bed contained many specimens of Mononchus and a few of Ironus ignavus, after ten days yielded no Mononchus, though it continued to yield Ironus, and in addition a few adult specimens of Tripyla and Monhystera, differences no doubt due in part to the fact that in stagnant collections Mononchus longicaudatus is subject to the attacks of a variety of fatal diseases caused by fungi and microbes. NEMAS A CLUE TO THE FLOW Nemas Unequally Distributed in Beds. The distribution of organisms in filter-beds is not uniform. For example, if a series of samples be col- lected, one each from near the main drain-pipe, near a lateral, between the laterals, and at the margin of the bed, the numbers and kinds of nemas will be found to differ in the various samples. This unequal distribution is doubtless a function of the flow of the water, for where the flow is rapid the biological environment differs from that where it is slower; there is a greater supply of oxygen, a greater supply of water- soluble food, and a greater supply of such free micro-organisms as may pass between the grains of sand. It follows that to some extent the 194 FILTER-BED NEMAS fauna and flora of filter-bed sand may be made a criterion of the rate and nature of the filtration. The general appearance of the sand in any particular part of the bed is a clue to the rate and nature of the filtration there, but this rough method is capable of refinement through the aid of a biological census. The difficulty is we do not yet know what significance to attach to the presence or absence of particular species. Should an attempt be made to devise and apply such a method, it might be found that the presence or absence of a few species would constitute a sufficient test. PARTIAL LIST OF THE NEMAS FROM AMERICAN SLOW SAND FILTER-BEDS* Achromadora minima Cobb Washington, D. C. Mononchulus ventralis n. g., n. sp. Actinolaimus radiatus Cobb... .Washington, D. C. Washington, D. C. Aphanolaimus ? Philadelphia Mononchus longicaudatus Cobb Apheltnchus ep Pittsburg Washington, D. C. Atylenchus sp New Bedford ,, , ,.. . . ,. Cephalobustp Philadelphia Mon h * Philadelplua Cylindrolaimus obtusus Cobb... Washington, D. C. Plectus clrratus Bastian Washington, D. C. Dorylaimus fecundus Cobb Washington, D. C. Prismatolaimus sp Philadelphia Dorylaimus sp Washington, D. C. Rkabditis sp Philadelphia Dorylaimus sp Philadelphia Rhabdolaimus sp Washington, D. C. Dorylaimun sp Philadelphia Spilophora sp Harrisburg Dorylaimus Bp Washington, D. C. Teratocephalus sp Pittsburg lota simile n. sp Washington, D. C. Trilobus longus Leidy Philadelphia. Ironus americanus Cobb Philadelphia THpyla monohystera de A/ an ... Washington, D. C. Ironus ionavus Bastian Washington. D. C. Tylencholaimus sp ^^ Bethlehem, Ironus longicaudatus de M an. . .Washington, D. C. p. , Monhystera subfiliformis n. sp . .Washington, D. C. Monhystera dispar Bastian Washington, D. C. Tylenchus filiformu Butschh (?) Monhystera sp Philadelphia Washington, D. C. Monhystrella plectoides n. subg., n. ep. Tylenchus sp Philadelplua Washington, D. C. Xiphinema americanum Cobb Philadelphia * The larger number of species from the Washington beds is due to the examination of a larger num- ber of samples than from beds elsewhere. The more important of these species are described below. The drawings are from nature and were made under the author's personal supervision by Mr. W. E. Chambers. MONONCHUS Bastian 1865 1. Mononchus longicaudatus Cobb (See p. 161). The feeding habits of Monon- chus are distinctly different from those of either of its frequent companions, Tripyla and Ironus. In capturing food Mononchus depends largely upon the grip of its powerful jaws. Tripyla depends upon its agility and its flexibility, and possibly coils itself about its victim, after the manner of a boa constrictor. Mononchus and Tripyla bolt their food, but Ironus feeds in an entirely different way; attaching its lips to its food, it rips a hole in the external layers by the outward stroke of its three, extremely sharp, radially acting onchi. As these move forward their points move outward, and two or three such movements serve partially to imbed the head of the Ironus. It would appear that then the more or less fluid parts only are imbibed, for the contents of the intestine of Ironus hardly ever present optically identifiable substances. It is manifest, however, that the contents of the intestine are animal in character, and so it seems beyond reasonable question that Ironus is carnivorous. I have never found the con- tents of the intestine to respond to the starch test. MONONCHULTJS VENTRALIS 195 Intro, vilam staining shows the existence of a dorso-ventral physiological differentiation in the intestine of Mononchus longicaudatus. Renette. When this well-known mononch was stained inlra vitam with trypan blue, the ampulla and a short portion of the duct of the renette was so distinctly seen as to leave almost no shadow of doubt that this portion of the renette structure is normal. I am inclined to think that the duct soon takes a lateral turn, and possibly becomes connected with the lateral field; thus far it has not been possible to follow it more than a distance mrfi p/i.. Fig. 1. Man- chulus ventralis, /*' , rl or til mil a very interesting nema, found in the Washington irltirtil filter-beds. The lateral fields are shown with great clearness; they fm are made up of about three rows of cells, d ar lat, each cell with an egg-shaped nu- cleus, nd ar lat. The intestinal nuclei, of about the same size, are shown darker. Oesophageal glands, sal, as in Mononchus. The small posterior gonad, appar- ently serving as a testis, is shown at 1st. Nearly the whole of the tostis is shown in the il- lustration. The spinneret is unus- ually large, and gives us for the first time some clue to the struc- w,,,.!,/ ture and me- a chanics of this organ. The de- tailsaremorefully illustrated in Fig. 2. For abbrevia- tions see p. 212. am of n-lm-liil ////// m . mr am . about equal to the radius of the nsck, so that the size and structure of the glandular part remain unknown. nlylcdl. MONONCHULUS gen. nov. Characters. Possessing the form and general appearance of Mononchus, but having the spinneret on the ventral side of the tail near the terminus, and the pharynx smaller and narrower with thicker walls, and with forward pointing onchi or teeth, of which a subventral one dominates. The labial papillae are smaller than is usual in Mononchus, in fact are barely visible. 196 FILTER-BED NEMAS The entire pharynx is about twice as long as the cavity bearing the onchi, but the posterior part is narrower and somewhat obscure. Anterior gonad reflexed. Posterior gonad outstretched, very small, producing spermatozoa. The development of the oocytes follows about the same course as that of the spermatocytes, which they resemble to a certain extent, though they are larger. Occasionally the oocytes so closely resemble the spermat- ocytes that it is rather difficult to make a clear distinction. The very youngest stages of the female gonad have not been seen, but in the youngest stages ob- served there were no indications of spermatozoa; yet at the same time sper- matozoa were developing in the minute posterior straight gonad. 2. Mononchulus ventralis n. sp. ^ ^7 ^ f^j trs' 1 The thick layers of the transparent, colorless, naked cuticle appear to be devoid of any but the very finest of transverse striae; but longitudinal striations are visible throughout the length of the body. Six rather thoroughly amalgamated lips of considerable thickness arch together over the pharynx and normally nearly close the mouth opening. There are six slightly spreading inconspicuous papillae scarcely interfering with the rounded contour of the front of the head; in addi- tion, surrounding the mouth, there are six forward pointing papillae. There are no eye-spots. Very inconspicuous amphids occur opposite the middle of the largest pharyngeal tooth in the form of small semi-circumferences opening back- ward and having a breadth about one-fifth as great as that of the corresponding part of the head. The anterior main thick-walled portion of the pharynx is about as long as the head is wide. When the pharyngeal organs are at rest this front cavity is comparatively well filled by the large, acute, forward pointing right submedian tooth. There are two other teeth, a small dorsal, for- ward pointing tooth having its apex near the middle of the pharynx, and an ex- ceedingly minute inward pointing tooth, or spur, in the left submedian portion of the cavity near the base. Opposite the anterior portion of the main tooth the walls of the pharynx are armed with several dozens of minute, rasp-like teeth or denticles. Close scrutiny of that part of the wall of the pharynx immediately behind the rasp-like area discloses that it is transversely striated to near the base. These pharyngeal striae can be seen only with the highest powers of the micro- scope under favorable circumstances. Behind this anterior portion of the pharynx is a narrower, unarmed portion, of equal length, making the total length of the pharynx about twice as great as the diameter of the head. The cells of the thick walled, narrow-lumened intestine contain scattered brownish granules. There are three unicellular caudal glands; two opposite each other immediately behind the anus, and a third, more or less dorsally located, behind and between the first two but emptying through a submedian ampulla and hence really sub- median. The single reflexed ovary, except when pushed forward by the presence of an egg in the uterus, reaches nearly back to the vulva. Habitat: This interesting digonic species has been found in peat soil, west of Fort Lauderdale, Fla., along a canal for drainage of land formerly covered with water, and at Miami, Fla.; in the sand of the filter beds at Washington, D. C.; and also in the Potomac River. A species that appears to belong to the genus Mononchulus is described by Daday under the name Prismatolaimus nodicaudatus, n. sp., in his "Mikro- skopische Siisswasserthiere aus Deutsch Xeu Guinea." MECHANICS OF THE SPINNERET 197 sub ait STRUCTURE OF THE SPINNERET I am not aware that anyone has ever attempted to explain the mechanism of Ihe spinneret of nemas. Manifestly the flow of the caudal secretion is controlled at will. Watching this operation as performed by a free-living nema, one is forcibly reminded of the facility with which spiders regulate the operation of their spinnerets, and, as in spiders, so in nemas, there must be a definite con- trollable mechanism for performing these operations. The structure of the spinneret in Mononchulus venlralis may at least suggest the mechanical prin- ciples exemplified. The Needle-Valve. As a rule the nema spinneret is so extremely minute that its details cannot be deciphered. In Mononchulus ventralis the spinneret is relatively large and its elements more or less resolvable, but since it is ventral in this species instead of terminal, as is usual, its form may not be entirely typical. In M. ventralis we find the duct of the spin- neret to end externally in a conical depres- sion near the end of the tail. This conical depression leads to a short oblique tube terminating internally at the valve of the spinneret, vlv-vlv, Fig. 2. The valve belongs to the class known as needle-valves, and the needle, if such it be called, is an acute, fusi- form affair, duplex in cross section, and nearly half as long as the terminus of the tail is wide. It is placed at an angle of about 45 degrees with the axis of the tail, and while its acute free distal end lies loose in a cavity of obverse mold, its more or less cephalated proximal end is connected with the dorsal side of the tail by means of oblique muscular fibres. The proximal part of the valve is located in the midst of a vesicle (?) to the dorsal side of which its proximal ex- tremity seems to be attached; the embryo- logical development has not been investi- gated, but conceivably the needle is formed by an invagination of the wall of the "vesi- cle." Into the base of the more or less ellipsoidal "vesicle" the ducts of the caudal ... glands empty. 1 he operation of the needle- part of the spindle-shaped valve is now easily understood. The internal body pressure will of itself keep the needle- Valve closed. Contraction of the muscular fibres already described serves to pull the needle loose from the mouth of the valve, and so permit an outflow of the secretion. The "needle" is composed of two elongated, ceratinous lateral elements joined side by side, and the orifice of the valve is composed of three elements, disposed in the form of a hollow cone about the distal half of the needle. Nervous Apparatus of Valve. Most of the foregoing features are shown in Fig. 2. Necessarily the apparatus is supplied with the appropriate sensory and motor nerves. The details of these latter have not yet been made out with x2ooo -::."."!