of Gastrotnchous Rotatoria. 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 Chcetonotus. 



M. Mecznikow* not only describes several species hitherto 

 imknown, but also makes known, under the names of Ghcetura 

 and Ce^halidiunij 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 Ga^trotrichaj an order which would form with that of the 

 Rotatoria a peculiar class in the subdivision of Vermes. Finally, 

 therefore, the Ichthydinia (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. Mecznikow f 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 imiting 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, 

 Chcetonotus (Ehrb.), Ichthydium (Ehrb.), Ghcetura (Meczn.), 

 Cejphalidiura (Meczn.) , Dasydites (Gosse) , Turhanella (Schlz.) }. 



* " Ueber einige wenig bekannte niedere Thierfomien, von Elias Mecz- 

 nikow," Zeitsclir. f. wiss. Zoologie, 1865, Bd. xy. p. 450. 



t ' Beobachtungen iiber Anatomie und Entwicklimgsgescliiclite wir- 

 belloser Thiere and er Kiiste von Normandie angestellt von Dr. E. Clapa- 

 rede/ Leipzig, 1803, p. 90, pi. 16. figs. 7-16; and " Bemerkungen iiber 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 Dujardinii and E. motioceretis. 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. 



X 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 



