ZOOLOGICAL AND BOTANICAL ASSOCIATION. 53 



2nd. Tho removal of the Rotifers and Entozoa to the Annulose sub- 

 kingdom. 



3rd. The separation of the Polyzoa from the Zoophytes, and the 

 recognition of the true molluscan affinities of the former. 



After the Radiata of Cuvier had been thus diminished, there still re- 

 mained an extensive assemblage of forms, which might, for convenience, 

 be defined as tho " Radiata of moderns." This sub-kingdom included 

 tliree classes, viz., Zoophyta, Acalepha, and Echinodermata. The 

 author then noticed the various points of structure in which the Echi- 

 nodermata differ from the other Radiata ; and showed that the two re- 

 maining classes agree in several distinct and characteristic anatomical 

 peculiarities, which justify the propriety of separating them from the 

 Echinodermata,* and uniting them into a sub-kingdom by themselves. 

 For this extensivo group Messrs. Prey and Leuckart have proposed the 

 term Ccelenterata. All the forms so designated possess in common this 

 anatomical character — namely, that the alimentary canal communicates 

 freely with the general cavity of the body. In many of the Ccelenterata 

 the peculiar bodies known as " thread cells" are developed; and from 

 the almost universal presence of these organs the term Kematophora 

 had been proposed for the same group by Professor Huxley, who, some 

 time since, from independent researches of his own, chiefly carried on 

 in the seas of the southern hemisphere, had arrived at conclusions pre- 

 cisely similar to those of Frey and Leuckart. The author then described 

 in some detail the leading structural peculiarities by which the Ccelen- 

 terata, as a whole, were distinguished, and maintained that they formed 

 a distinctly circumscribed and most natural sub- kingdom, comparable 

 in this respect with cither the Mollusca or Vertebrata. So far it had 

 been shown that the Ccelenterata included the forms usually known as 

 Zoophy tcs and Acalephs, but it must not be supposed that these are the 

 names of tho two classes into which this sub- kingdom ought to be di- 

 vided. Two obvious modifications of structure serve to separate it into 

 as many distinct divisions. In the first of these, termed Hydrozoa, the 

 wall of the digestive canal is in close contiguity with that of the general 



* The separation of the Ccelenterata from the Echinodermata is a consideration alto- 

 gether independent of tho more difficult question, — What Li the true position of the 

 latter? For a solution of this most important problem Science is much indebted to the 

 able researches of Professor Butler. 



