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." 



