of Gastrotrichous Rotatorta. 215 
plained, as that naturalist only knew Echinoderes from a bad 
figure of Dujardin’s. After the recent investigations on this 
singular type, Mr. Gosse would no longer think of approxi- 
mating it to Chetonotus. 
M. Mecznikow* not only describes several species hitherto 
unknown, but also makes known, under the names of Chetura 
and Cephalidium, two very remarkable new genera evidently 
nearly allied to the preceding. This naturalist reviews all 
the previously expressed opinions as to the zoological position 
of this singular group; he discusses them carefully, and ends 
by rejecting them. He himself resolved to erect the genera 
that we have enumerated into an order apart, under the name 
of Gastrotricha, an order which would form with that of the 
Rotatoria a peculiar class in the subdivision of Vermes. Finally, 
therefore, the Jchthydinia (for that is the name which has been 
most generally given to them), after having been tossed about 
in every direction on the ocean of classification, return to drop 
anchor nearly at their starting-point. 
The opinion maintained by M. Mecznikowt has a good 
deal in its favour. In any case, I accept his order of Gastro- 
tricha, characterized essentially by the clothing of vibratile 
cilia on the ventral surface of the body, and also by some other 
secondary characters, such as the absence of jaws &c. The 
affinity of this order with the Rotatoria also appears to me to 
be incontestable. The convenience of uniting all these ani- 
mals in one class will then be the only subject of discussion. 
We know, moreover, that naturalists are still divided in opi- 
nion on the subject of the natural position to be assigned to 
the Rotatoria. 
Putting on one side the latter question, we find the order of 
the Gastrotricha composed at present of six genera, namely, 
Chetonotus (Khrb.), Ichthydium (Ehrb.), Chetura (Meczn.), 
Cephalidium (Meczn.), Dasydites (Gosse), Turbanella(Schlz.)t. 
* “Ueber einige wenig bekannte niedere Thierformen, von Elias Mecz- 
nikow,” Zeitschr. f. wiss. Zoologie, 1865, Bd. xv. p. 450, 
+ ‘Beobachtungen uber Anatomie und Entwicklungsgeschichte wir- 
belloser Thiere and er Kiiste von Normandie angestellt von Dr. EK. Clapa- 
réde,’ Leipzig, 1863, p. 90, pl. 16. figs. 7-16 ; and “ Bemerkungen tiber Echi- 
noderes von Elias Mecznikow ” (Zeitschr. f. wiss. Zoologie, 1865, Bd. xv. 
4tes Heft, p. 458). In the work cited I described two species under the 
names of Echinoderes Dujardinit and E. monocereus. A year later, with- 
out knowing of my observations, Mr. Gosse renamed the former of these 
species; but as he likewise dedicated it to Dujardin, this does not cause 
any inconvenience in synonymy. Mr. Gosse writes it Echinodera, and 
not Echinoderes. 
} It is just to say that M. Perty, without discussing the question with 
the same care as M. Mecznikow, nevertheless arrived at nearly the same 
