236 
■ ALFRED GTARD. 
3. Intoshia leptoplance. — Parasitic in Leptoplana tremeU 
laris. Length 0-135, breadth 0 03 mm. 
This last species, like the preceding, is regularly cylin- 
drical, and rounded at the extremities. According to the 
figure of Keferstein, it presents ten metameres, perfectly 
regular, in addition to the cephalic and caudal rings. The 
endoderm appears to be formed by large spherical cells. 
The general form of the body, the regularity of the 
metamerisation in the two species parasitic in the Nemertean 
and the Planarian, lead to the supposition that there may 
be other differential characters present in them, which would 
lead zoologists probably to create a particular genus for 
these two types. Such a step in our present state of know- 
ledge would, it appears to me, be superffuous. 
Metschnikoffi has recently described, under the name of 
Rhopalura Giardii, a new species of Orthonectida, w'hich he 
has since identified with Rhopalura ophiocom<B. 
This species, which is parasitic in Amphiura squamata, 
was found abundantly at Spezzia. It presents itself in two 
different forms, which Metschinkoff" thinks are probably 
identical with Rhopalura ophiocomce and Intoshia gigas, 
which, according to him, are merely the male and female of 
one species. 
I must confess that this idea has often occurred to me 
during my researches, and I do not entirely give it up even 
at this moment. The strongest argument in its favour is 
that the two forms, Intoshia and Rhopalura^ exist in about 
the same quantity in Ophiocoma neglecta ; and that it would 
be curious to find in this little Ophiurid two different repre- 
sentatives of a group so rare as are the Orthonectida. At 
the same time, the difference between the two forms is 
greater than I had at first supposed. Further, we have not 
elsewhere any example of an animal in which some females 
produce eggs, giving birth to males exclusively, and others 
eggs from which only females issue. We might, perhaps, 
try to remove the difficulty by supposing that, in one or the 
other case, there was parthenogenesis (arrenotoky or thely- 
toky) ; but this would be, at present, pure hypothesis. 
However this may be, I have no fundamental objection, to 
such a mode of explaining the facts, but I shall wait to 
make up my mind for the time when I shall have found in 
another species of Intoshia {Intoshia lineiy for instance) an 
accompanying form analogous to Rhopalura. 
Without doubt sexual differences, such as exist \n Bonellia 
viridis, and in other worms, such as Bilharzia hcematohia, 
* ‘ Zoologischen Anzeiger,’ II, No. 40, and No. 43, 
