MECZNIKOW, ON ICHTHYDIUM, ETC. . 245 
In the same example of Chetonotus larus I found in 
the cavity of the body a number of eggs from 0°19 mm. to 
0:026 mm. long, which were without the egg covering, and 
were observed in the process of segmentation. We may 
consider these hitherto unknown forms as summer eggs. 
The winter eggs which have already been examined by other 
naturalists have, as is known, other characters; they are in 
the same species of which I examined the summer eggs, 0°06 
mm. long, and have a thick shell. 
As to the male generative organs of our animals I still 
remain in the dark ; but still I retain the hope of finding out 
their relation through other experiments. I can only put forth 
the supposition that certain cellular bodies which I found in 
some individuals of Chetonotus represent the male genitals. 
This supposition cannot be proved, but still it is possible that 
our animals, as the Rotatoria, show a sexual dimorphism, 
and that the rare male has till now entirely escaped me. 
Amongst different alge, Infusors and Rotatoria, I once 
found a few eggs which were 0:02 mm. to 0:033 mm. long, 
and which were provided with a pretty thick shell, whose in- 
side contained a perfectly formed, lively embryo in a bent-up 
position. These embryos, which belonged to Ichthydium 
podura, were perfectly like their parents, and were only to be 
distinguished from them by wanting the generative organs. 
This remark is at least interesting, because it shows the 
absence of any metamorphosis in the Ichthydina. 
Having made these incomplete remarks on the interesting 
family of Ichthydina, I shall allow myself to make some 
observations on the systematic position, that is, the relation- 
ship of these animals. 
Ehrenberg has already made known that the Ichthydina 
differ from the Rotatoria in many respects, an idea which 
Dujardin takes up much more strongly, separating our 
animals entirely from the Systolids. The difference between 
these two groups is in the absence of the jaws and a resistent 
body-covering in Ichthydina, and in the want ‘de cette con- 
tractilité, qui est tout-a-fait caractéristique chez les Systo- 
lides.” Although the first point, namely, that of the absence 
of jaws in Ichthydina, on the whole is quite right, yet I do 
not think that we can consider this character as an impor- 
tant one, because we know for certain that the Rotatoria show 
a great variety in their digestive organs. I need scarcely re- 
mind you of the male, who is completely without these organs, 
or of the presence or absence of the anus in different forms 
of Rotatoria. We know, too, that the jaws which are con- 
stantly present in the female show often a striking variation, 
