ON THE ANGUILLULIDÆ. 129 
one elongated near its middle, and the other terminal, rounded, and containing a 
simple valvular apparatus. Intestine rather sparsely covered with fat-particles, 
the large containing cells of which can sometimes be recognized. Yulva near the 
middle of body. Uterus bifid, segments symmetrical. Oviparous or viviparous. 
Spicules of moderate size, slightly curved. Accessory piece single, posterior, me- 
dian, about half as long. Caudal ale lateral, membranous, supported by sets of 
rays. Ventral gland wanting. Lateral vessels or cellular canals not seen. 
Movements active. 
Although I have looked very carefully for them, I have been unable to distinguish 
either lateral vessels or the ventral exeretory gland in any of the representatives of this 
genus. 
The typical Rhabditis terricola of Dujardin seems undoubtedly to correspond as re- 
gards structural details with the other species that I have placed in this genus; and, 
since it is now evident that Dujardin associated with this animal others of such diverse 
types as Anguillula aceti and Tylelenchus tritici, we shall have the less difficulty in 
imagining that he may have confounded with them also members of the genus Plectus, 
not only because they seem to be much more abundant than are the proper representa- 
tives of the genus Rhabditis, but also because he speaks of the latter as possessing that 
remarkable tenacity of life which belongs to species of the two former genera, when, 
as far as my experience goes, it is not possessed by the real allies of the typical Bhab- 
ditis terricola. 
1. R. MARINA, n. sp. (Plate X. figs. 60-62.) 
Female, length +”, breadth 434". 
External Characters.—Body tapering considerably anteriorly, but more posteriorly, 
Where it narrows to a point. Head truncate, naked. Integument having transverse 
and longitudinal striæ, those of each set being about 10900 apart. 
Pharyngeal cavity cylindrical, Ir long. (Esophagus $th of total length, containing 
in its terminal enlargement a valvular apparatus, which may be seen to open and shut with 
spring-like rapidity for the passage of fluids. Posterior part of cesophagus and anterior 
portion of intestine fixed to parietes by distinct muscular retinacula. Intestine much 
larger at commencement than terminal part of œsophagus; covered spar sely with fat- 
particles, the containing cells of which can occasionally be recognized. Anus 555 from 
posterior extremity. Vulva slightly posterior to middle of body. Uterus bifid; seg- 
ments symmetrical, large, and densely distended with freely moving young and Ure m 
all stages of development. Ova 4lg" long, by see” broad. Gland-system very slightly 
developed ; but numerous floating gland- or blood-cells in cavity of body, the maximum 
Size being about x4..." in diameter!. 
Male, length 44", breadth aio - | 
Anus zig from posterior extremity. Genital tube consisting of a single testicle, 
| I have observed (in the female only) what appear to be two lateral apertures through the integument, connected 
mth an obscure appearance of oval vesicles or dilatations internally, situated exactly midway between the anus and 
Posterior extremity, | 
VOL, xxv, S 
