IS Huxley on Lacinularia socialis. 
In N. aurita^ however, as it appears from Mr. Gosse's de- 
scription, and in Brachionus polyacanthus (figs. 30-33), several 
processes, three in the latter case, are developed from the 
superior pre-trochal region. They are richly ciliated, and 
appear to represent the accessory circlet of Lacinularia. 
Another distinct type is presented by Philodina (^figs. 34- 
37). In this the great trocha is bent upon itself, and the 
anterior divison of it, at first sight, simulates an accessory 
circlet developed in the superior pre-trochal region. It is not 
so, however, as the continuity of the band of cilia can be 
readily traced throughout. 
To this division of the Rotifera, viz. those which have the 
anus on the same side of the body as the ganglion, appear to 
belong the genera Stephanoceros and Floscularia — at least, 
if the ganglion be what I believe it to be, a granular mass, 
in connexion with the upper part of a large oval mass com- 
posed of clear cells, and having a pit in its centre exteriorly, 
which I believe to be the altered ciliated sac. 
These might then be considered as Notommatae whose 
trochal circlet had become produced into long processes in 
Stephanoceros, while they remain as shorter knobs in Flos- 
cularia ; a tendency to which development may be traced in 
the little processes into which the trochal circlet is thrown 
around the mouths of Lacinularia and Melicerta, and perhaps 
in the three processes which, according to Mr. Dalrymple, 
arch over the mouth in Notommata. 
But Stephanoceros, Philodina, Notommata, Brachionus, and 
Lacinularia are the types of the great divisions of the Rotifera, 
and whatever is true of them will probably be found to be 
true of all the Rotifera. 
We may say, therefore, that the Rotifera are organized upon 
the plan of an Annelid larva, which loses its original symmetry 
by the unequal development of various regions, and especially 
by that of the principal ciliated circlet or trochal band ; and it 
is curious to remark that, so far as the sexes of the Rotifera can 
be considered to be made out (approximatively), the dioecious 
forms belong to the latter of the two modifications of the type 
which have been described, while the monoecious forms belong 
to the former. 
It is this circumstance which seems to me to throw so clear 
a light upon the position of the Rotifera in the animal series. 
In a Report in which I have endeavoured to harmonise the 
researches of Prof. Miiller upon the Echinoderms^* I have 
,shown that the same proposition holds good of the latter in 
Annals of Natural History, 1851. 
