Maupas_1900

Measurements:

The body of the adult females (pl. XXII, fig. 1), cylindrical and relatively thickset, tapers gradually towards both extremities. In the front, it is truncated by the mouth; in the rear, it thins out in a fine tip. It has a general opaque blackish aspect, caused by the many birefringent corpuscles contained in the width of the intestinal cells.

The cuticle, colorless and thick, appeared to me smooth and without striations; but De Man describes a fine striation in the anterior region of the body. He has moreover observed wide lateral membranes.

The mouth (pl. XXII, fig. 2) is not made of fleshy lips, as in the other Rhabditis. It is equipped with two pairs of chitinous appendages, of very different shapes for each pair. The exact conformation of these appendages is difficult to grasp because of their smallness, and like De Man, I do not pretend to have reached a rigorously certain view. A first pair, shorter but thicker and more chitinized, strikes by its opaque blackish aspect. Each appendage appeared to me to have the shape of a wide and irregular hook (see the figure), ending in a rather fine tip. The appendages of the second pair, longer and protruding more towards the front, present the aspect of thin transparent strips, in the shape of a quarter of circle and very finely striated and pectinate on their edge. This description

MODES AND FORMS OF REPRODUCTION OF NEMATODES. 83

matches that of De Man for the number of appendages and their division in two pairs differing by their shape.

The buccal cavity is comparatively very long. It indeed equals a quarter (De Man says a fifth) of the esophagus length, measured from the anterior extremity of the mouth. Its shape is that of a regular cylinder with walls that are rather thin than thick. In the rear, it directly connects to the esophagus, without the narrowing and thickening that are usual for Rhabditis.

The esophagus (pl. XXII, fig. 3) presents the usual conformation, except for the absence of an anterior bulb. The anterior part of the esophagus bulges gently until the narrow neck, without a distinct bulb. Cobb and De Man, however, mention and describe it as having a barely-bulged, elliptical, shape. The posterior bulb is regularly rounded and its valves (teeth) are well developed. In the front, the esophagus does not extend as a sheath enveloping the buccal cavity as in most Rhabditis.

The female tail (pl. XXII, fig. 1), starting from the anus, tapers gradually to thin out in a fine tip.

In addition to the albumino-fatty granulations, the cells of the intestine always contain many birefringent granules, of spherical shape and rather voluminous. These corpuscles give the intestine its opaque blackish aspect. – The rectum has at the level of its insertion with the intestine a length equal to the body width. The rectal glands, one dorsal and one ventral, are well developed.

The nerve ring (pl. XXII, fig. 3, c), of fibrous structure, envelops the neck of the esophagus slightly above the second bulb. It bends obliquely towards the ventral side and sends out extensions towards the excretory pore.

The excretory organ (pl. XXII, fig. 3, p) is very difficult to see. I only succeeded in distinguishing the pore and the unpaired canal that leads to it, which are located at the level of the posterior bulb; I could not see anything of the lateral canals.

The vulva (pl. XXII, fig. 1, v) is located rather exactly towards the middle of the total length of the body, its lips are clearly thickened. The vagina is short. The paired genital tube (pl. XXI, fig. 9) is relatively little developed, its extreme bends end at a large distance from the two extremities of the intestine. The uterus is wide and alone makes almost half of the genital tube. Nonetheless, it only ever contains one egg, and the two uteri always alternate, one being empty while the second is filled. At its anterior extremity, it forms a diverticulum with the shape of a sac serving as seminal receptacle. The vitellogen and germigen merge, and only a single maturing ovum can ever be seen. The folded part of the ovary is very short and appears like the hook of a crook.

The eggs (pl. XXI, fig. 10), of oblong shape, measure 52 μ in length and 20 μ in width. They are regularly rounded at the extremities, which sometimes appear slightly bulged. The shell is thick and bears fine little spikes.

The male tail (pl. XXI, fig. 11) belongs to the peloderan type (De Man says leptoderan), that is, the bursa fully envelops the caudal extremity. The base is narrow and opened in the front. The papillae, numbering 7 pairs, are spaced apart rather regularly, without forming any particular groupings. Only two are preanal and the last one in the front is inserted at the level of the middle of the length of the spicules.

The spicules (pl. XXI, fig. 11), of a dark brown color, are arched and thickset. In the rear, they end in a fine tip, in the front by a

MODES AND FORMS OF REPRODUCTION OF NEMATODES. 85

clearly narrowing head. They are independent of each other. The gubernaculum (accessory piece) is thick and equals in length half that of the spicules.

The testis does not present anything noteworthy. The spermatozoa, whether of masculine or of feminine origin, are perfectly identical to each other. Of spherical shape and very small, they measure 1 μ to 1.5 μ. Their substance appears to be reduced to the nucleus only and their aspect is homogeneous.

Rhabditis coronata is essentially oviparous. In the uteri, there is only a single mature egg at a time, alternatively in each uterus. The eggs do not remain in the uterus but are laid as soon as the shell is developed and before the division into two blastomeres. The layings follow each other slowly. At a temperature of 21° C., an isolated female laid only six eggs in 24 hours. These eggs, at the same temperature, take three full days to develop until hatching.

I have not gathered any observations on the total number of layings, nor on the length of the larval growth and lifespan.

The movements of this nematode are very slow and heavy. In the waterdrops in which it is raised, it wriggles about slowly by contorsions, but without moving forward nor circulating.

On several occasions, I isolated juveniles before adulthood, in a total of about 150 individuals. All became females, which laid fertile eggs that developed regularly. When examined under the microscope at high magnification, all these females presented a seminal receptacle that was stocked with small spermatozoa identical to those of the males. No doubt can therefore remain: the species is protandrous autogamous hermaphroditic.

I did not make any methodical cultures to ascertain the frequency and the ratio of males. However, from approximations found in my

notes, I believe that I can state that no more than 5 to 6 per 1,000 individuals can be found. It is very probable that, here as in the previous species, these rare males do not play any role in the reproduction of the species. But I have not performed any experiment regarding this point.

Cobb does not even mention the existence of males. De Man says to have encountered a single one, among a very large number of females.

DIPLOGASTER ROBUSTUS mihi

I found this species only once, in black soil sampled under the pinetrees of the higher part of the experimental garden at the Hamma near Algiers. I could make it multiply at will on depression slides, feeding it with rotten flesh.

Measurements:

The size of adult females can vary from 1,390 μ to 2,490 μ; that of the males from 1,320 μ to 1,400 μ.

The body of females (pl. XXII, fig. 4), thick and robust, is slightly bulged in its middle part. It tapers gradually and slowly towards the extremities. In the front, it is truncated by the mouth; in the rear, it thins out in a fine tip. Its general aspect is opaque blackish, because of the many granulations of the intestine.

MODES AND FORMS OF REPRODUCTION OF NEMATODES. 87

The cuticle is colorless, transparent and rather thick. It is decorated with fine longitudinal veins that are characteristic of Diplogaster. These veins, numbering 34 to 36 in the middle region, are composed of two rows of fine punctuations (pl. XXII, fig. 5). In addition to these longitudinal veins, an extremely delicate transversal striation, with one stria for two punctuations of the veins, can also be perceived in favorable situations. These striata, at the crossing of the veins, also resolve into two or three very small punctuations.

The mouth (pl. XXII, fig. 6) ends the anterior extremity without protuberance or constriction of any sort that would distinguish it from the rest of the body. It is lined by six small and little-salient lips, each equipped with a fine papilla. The buccal cavity, wider than deep, has rather thick chitinized walls. Two little-salient conical teeth are found at the bottom.

The esophagus (pl. XXII, fig. 7) presents the usual conformation. The anterior half is of one third longer than the posterior half. The anterior bulb, of a slightly elongated shape, is well developed. Its internal valvular walls are strongly chitinized. The rounded posterior bulb always displays two large clear and nucleolated nuclei within its fleshy substance.

The female tail (pl. XXII, fig. 8), starting from the anus, thins out gradually in a long, thin and tapering cone. It bears a pair of fine lateral papillae that are rather difficult to see and are inserted behind the anus at a slightly longer distance than the length of the rectum.

The intestine, in well-fed individuals, always has an opaque blackish aspect, caused by the many granulations that accumulate and are stored in the constitutent cells of its wall. Some of these

granulations are of albumino-fatty nature; the others with a crystalline birefringent structure. The latter can be very abundant, and they are mostly responsible for the great opacity. The rectum has at the level of its junction with the intestine a length equal to the body width. At this junction, it is endowed with well-developed dorsal and ventral glands.

The nerve ring (pl. XXII, fig. 7, c), of fibrous structure, envelops the narrow neck of the esophagus above the second bulb, bending obliquely towards the ventral side and sending out extensions towards the excretory pore.

The excretory organ (pl. XXII, fig. 7, p) is easy to distinguish. The pore and unpaired canal are located at the posterior level of the second bulb. The anterior lateral branching is very sinuous, with short sinuosities; it can be followed without effort beyond the front end of the anterior bulb. The posterior canal is almost straight and I could follow it until the vicinity of the rectum. At the point of merging of these canals with the unpaired canal are found two unicellular glands, each provided with a large and clear nucleus with an opaque nucleolus.

The vulva (pl. XXII, fig. 4 and 9, v) has the shape of a round and narrow opening, without protruding lips. It always opens on one of the longitudinal veins, the diameter of which it barely exceeds when closed. The vagina is relatively developed and presents the aspect of a narrow tube, directed in the transversal direction within the body.

The paired genital tube is greatly developed (pl. XXII, fig. 4 and 9), its extreme bends come quite close to the two extremities of the intestine. The uteri are wide and spacious; they continue into a narrow oviduct (tuba). The latter, in the very young females (pl. XXII, fig. 9) that still have only one or two eggs in each uterus, runs

MODES AND FORMS OF REPRODUCTION OF NEMATODES. 89

directly without sinuosities until the extremity of the ovary, to which it connects by making its extreme bend. But in the older females (pl. XXII, fig. 4) whose uteri are crammed with eggs, the oviduct, being hold back by the bloated uterus, folds on itself. There is no special pocket serving as a seminal receptacle. The spermatozoa are stored (pl. XXII, fig. 9) in part in the uterus, and in part in the ovary, at the junction points of these two organs with the oviduct. The ovaries proper do not form bends, but directly extend along the length of the body, simply orienting obliquely across it, in order to fit alongside the intestine. The free extremity of each of them extends largely beyond the vulva and almost reaches the head of the opposite ovary. The distinction between the germigen and the vitellogen can only be made by the development of about twelve big ova in the latter.

The eggs (pl. XXII, fig. 10), of an oblong shape rounded at the extremities, measure 79 μ in length and 46 in width. Their shell is fine and smooth.

The male tail (pl. XXIII, fig. 1), in its general conformation, completely resembles the female tail. It extends and gradually tapers into a long and thin cone. It is provided with a small, narrow and little-protruding bursa, which extends in the front and in the rear of the anus at distances that exceed somewhat the length of the spicules. There are 10 pairs of papillae: first, completely in the rear towards the extremity of the first third of the tail, three small papillae in a tight group, inserted onto the ventral side of the tail; then three other stronger papillae, laterally inserted between the anus and the previous ones and consequently postanal like the latter; the two next ones inserted very closely in front of the anus, laterally one above the other; finally number 9 at the level of the anterior extremity of the spicules and number 10 still further

anteriorly, at a distance equal to the length of the spicules. All these papillae, safe for the three small posterior ones, are strong, conical and clearly show a central neuro-muscular net. It seemed to me that in addition to these ten paired papillae, there was still an unpaired one on the anterior lip of the cloacal opening.

The spicules (pl. XXIII, fig. 2), thin and very arched, are slightly colored with a smoky brown. They end in the front by a rounded head, in the rear in a fine tip. The gubernaculum (accessory piece) equals in length the third of the spicules. Very thin in the rear, it suddenly thickens in its anterior third. – In one of the only three males that I encountered, the spicules presented irregularities, one being one third shorter than the other, and of somewhat anomalous shape. We already noted above analogous anomalies in the males of

Rhabditis dolichura.

The testis is conformed according to the usual type in rhabditids. In one of the males, which I kept alive for eight days during its full maturity, it was transformed into a vast seminal reservoir, from the vas deferens until almost the anterior bend. This entire length was packed with spermatozoa that were piled upon each other. Next to the bend, the spermatoblasts still continued to transform themselves into spermatozoa, dividing twice. In the middle of this mass of spermatozoa were irregularly scattered many crystalline needles (pl. XXII, fig. 11) of a length of 14 to 50 μ. These needles sometimes end in a fine tip, sometimes are truncated as if broken. They had no morphological relationship to the spermatozoa and had doubtless formed there following some chemical reaction. They probably represent a residual substance that has accumulated in the seminal reservoir. When treated with acetic acid, they dissolved without