248 MECZNIKOW, ON ICHTHYDIUM, ETC. 
parison of the two groups of animal. Concerning the former 
we must admit that the bottle-shaped forms of Cheto- 
notus, Ichthydium, and Cephalidium, are like no forms of 
Rotatoria; but, on the other hand, we may add that our 
Chetura bears a great resemblance to certain soft wheel 
animals, for example, to Notommata tardigrada. The furcal 
appendages of our Ichthydina find analogous forms only in 
the Rotatoria. The similarity of form of the vibrating 
apparatus, which becomes apparent especially on comparing 
the interesting ciliated apparatus in Cephalidium with certain- 
wheel animals, I have mentioned and considered as a point 
of relationship between the two animal groups. The presence 
of two kinds of eggs in our animal speaks strongly for my idea ; 
-as regards the other organs, we can satisfy ourselves if we 
remember the above critique on the ideas of other naturalists. 
We add only one more proof, namely, that the highly 
developed sensory organs in the Ichthydina agree with the 
same structures in the Rotatoria. The relationship between 
the two groups cannot be carried into details. The 
absence of jaws, and the presence of ventral cilia, in the 
Ichthydina, together with a few secondary properties, show 
striking differences between them. If we reckon all these 
circumstances together, we come to the conclusion that 
the Ichthydina form a small group of themselves, which is 
related to the Rotatoria, and is best named Gastrotricha. If 
we call the wheel animals after their most striking character, 
Cephalotricha, then we can perhaps not unfittingly form 
a new class out of these two orders, which possess some re- 
lationship with the Vermes, and a still more distant one with 
the Arthropods. 
The arrangement of the Gastrotricha consists at present of 
six genera:—Chetonotus (Ehrenb.), Ichthydium (Ehrenberg), 
Turbanella (Schultze), Sacculus (Gosse), Chetura (Mihi), 
and Cephalidium (Mihi). 
II. Remarks on Ecuinoprres.—Dujardin has described 
under this name a remarkable animal which he found at 
St. Malo, which appeared to be related to the Worms as well 
as the Rotatoria and lower Entomostraca. The same animal 
was found by Leuckart in Heligoland, and was considered to 
be a Dipterous larva. Claperéde has lately made some further 
remarks concerning this creature, which he calls Hchinoderes 
Dujardinii, and has added some remarks on a second new 
form, namely, Echinoderes monocercus. 
I have found and examined both the species mentioned, in 
Heligoland ; but, nevertheless, have found nothing which can 
