of Gastrotrichous Rotatoria. 219 
thirds are simply filiform. Properly speaking, it would appear 
that we ought to regard this pouch as a seminal vesicle rather 
than as a testis; for I have only seen mature zoospermia in its 
interior. But I have found no other organ capable of being 
regarded as a male sexual gland. ‘The deferent canal is 
always filled with zoospermia, and issues in a penis. This 
organ is formed by a vesicle full of a granular liquid, and by 
a spicule perforated by a canal along its axis. The point is 
directed towards the sexual pore, which is itself protected by 
two little plates. I have not been able to see ovaries, properly 
so called. An isolated egg in various stages of growth has 
alone met my eyes; sometimes there have been two of them. 
The mature ovule is oval, and its vitellus granular. The 
greater axis attains a length of 0-088 millim. The germinal 
vesicle ordinarily contains two spots. There is no special 
female pore ; the sexual pore that I have described leads, in all 
probability, into an atrium common to both the male and the 
female apparatus. 
The hermaphrodism of Hemidasys agaso deserves parti- 
cular notice. M. Max Schultze had already thought that 
the Gastrotricha were hermaphrodite. This opinion has been 
combated in the most positive manner by M. Mecznikow. In 
all the other Gastrotricha the male elements have only been 
met with exceptionally; and M. Mecznikow supposed that the 
simultaneous presence of zoospermia and ovules noticed by 
M. Schultze was to be explained as occurring in fecundated 
females. In Hemidasys agaso, on the contrary, the presence 
of zoospermia is the rule, and its hermaphrodism is incon- 
testable. 
I conclude this article with a diagnosis of the genus :— 
Genus HEMIDASYS. 
Gastrotricha of a lineal form, with a vibratile coat restricted 
to the anterior region of the ventral surface. Body armed 
with a certain number of conical ventral appendages, which 
contain in the axis a prolongation of the parenchyma. 
Species Hemidasys agaso, Clprd. 
Inhabits the mud of the harbour of Naples, voluntarily fixing 
itself to the body of Neretlepas caudata, Delle Chiaje. 
