LACINULARIA SOCIALLS I43 



Stephanoceros and Floscularia — at least, if the ganglion be what I 

 believe it to be, a granular mass, in connection with the upper part of 

 a large oval mass composed 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 Notommatse whose trochal 

 circlet had become produced into long processes in Stephanoceros, 

 while they remain as shorter knobs in Floscularia ; 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 

 Llelicerta, and perhaps in the three processes which, according to Mr. 

 Dalrymple, arch over the mouth in Notomviata. 



But Stephanoceros, Philodina, Notoimnata, Brachionus, and Lacinu- 

 laria 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 (approximately), 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 I have shown that the same proposition holds 

 good of the latter in their larval state, and hence I do not hesitate to 

 draw the conclusion (which at first sounds somewhat startling), that 

 the Rotifera are the permanent forms of Echinoderm larva, and hold 

 the same relation to the Echinoderms that the Hydriform Polypi hold 

 to the Medusa:, or that Appendicularia holds to the Ascidians. 



The larva of Sipunculus might be taken for one of the Rotifera ; 

 that oi Ophiura is essentially similar to Stephanoceros ; that of Asterias 

 resembles Lacinularia or Melicerta. The pre-trochal processes of the 

 Asterid larva Brachiolaria are equivalent to those oi Brachionus. 



Again, the larvae of some Asterid forms and of Comatula are as 

 much articulated as any Rotifera. 



It must, I think, have struck all who have studied the Echinoderms, 

 that while their higher forms, such as Echiurus and Sipunculus, tend 

 clearly towards the Dioecious Annelida, the lower extremity of the 

 series seemed to lead no whither. 



' Annals of Natural History, 1851. 



