— 335 — 



their great length to distinguish this new form from its allies, that 1 hâve 

 selected the spécifie title bisetosum for the créature. 



The mouth is a permauently projecting tube, surrounded by a ring, at the 

 extrême front of the head. It is continued into a long œsophagus, about 

 one-third the total length of the animal, having a narrow, but distinct, 

 straight lumen, and very thick walls, on which I could deteetno rross-stria- 

 tion. The gullet terminâtes, at the point where the neck passes into the 

 trunk, in a long straight stomach, running along the ventral side of the 

 body-cavity, and crowded with colourless food in pellets: this is continued, 

 without any visible constriction, into the intestine, and ends in the anusjust 

 in front of the rounded posterior extremity of the trunk. 



I could not détermine the présence of the water-vascular canals and con- 

 tractile vesicle ; almost : certainly thèse exist, but are exceedingly diflicult 

 to observe. 



Dorsally to the stomach is situated a fairly large, colourless body, exhi- 

 biting a central nuclear vesicle ; this body was formerly thought to be the 

 ovary, but Dr. Zelinka has shown that the true ovaries in the Gastrotricha 

 are paired organs placed near the venter, one on each side of the intestine 

 (Unis corresponding in position with the paired ovaries of the family Philo- 

 dinidae of the Rotifera). The large dorsal body is a developing ovum; 

 whether this is contained within an oviduct having extremely délicate mem- 

 branous walls, or simply lies freely in the perivisceral cavity, is doubtful, 

 as also is its mode of exit from the body. 



The créature swims actively with an even gliding motion through the 

 water; in no case did I observe any jerking or springing, the weak body- 

 spines being probably useless for such a mode of progression. 



The head is often freely moved up and down upon the neck, but has not 

 the constant drooping appearance (in side aspect) noticeable to D. fusi- 

 f or mis. The latéral lobes seem capable, to some extent at least, of being 

 protruded or relracted at the creature's will ; at certain times, the outline of 

 the head appeared quite conical, or very faintly five-lobed (cf. the figures), 

 while at others, the same animal presented the distinctly three-lobed out- 

 line of the head already described. 



The présent species approaches in ils gênerai outline D. longisetosum 

 (Metschn.), but is at once separated from the latter by the relative lengths 

 of the body and caudal bristles. The latter are, in longisetosum, shown 

 much less than half the length of the latéral body-setae (which are described, 

 as «very long and stout »), and altogether lack the conspicuousness they 

 attain in bisetosum. The présent form is also nearly twice the size of 

 Metschnikoff's species, and other différences exist which I think fully justify 

 me in regarding bisetosum as specifically distinct. 



The entire animal is quite colourless; length, excluding caudal setae 



about — — inch. 



In col I .sion, the same pond has furnished me, on other occasions, with 

 pecimens of Dasydytes fusiformis Spencer and Lepidoderma rhomboides, 

 Stokes (the latter only recorded, hitherto, from Trenton, New Jersey) 

 while at Chingford I bave met with Dasydytes goniathrix Gosse and 1). fusi- 

 formis Spencer. 



