xvn POLYZOA AND BRYOZOA CLASSIFICATION 475 



animals. This was principally due to the observations of J. V. 

 Thompson l in Ireland, who introduced the term POLYZOA ; and 

 of C. G. Ehrenberg 2 in Germany, who proposed the class-name 

 BRYOZOA, or moss-like animals. 



It is impossible to avoid all mention of the controversy which 

 has raged with regard to these two rival terms. The contro- 

 versy is for the present at rest, the name Polyzoa being 

 employed by the majority of English writers, amongst whom 

 must be mentioned Allman, Busk, Hincks, and Norman, ad- 

 mittedly authorities of the tirst rank ; while Bryozoa is 

 employed by practically all the Continental writers. 



The priority of Thompson's name is unquestioned. While 

 Ehrenberg, however, definitely introduced Bryozoa as the name of 

 a group, Thompson was less precise in this respect, although he 

 states 3 that his discovery "must be the cause of extensive 

 alterations and dismemberments in the class with which they 

 [the Polyzoa] have hitherto been associated." Thompson, in 

 fact, clearly understood that the Polyzoa could no longer rank 

 with the Hydroids. The controversy has been summarised by 

 Hincks, in his History of the British Marine Polyzoa* where 

 references to other papers on the same subject are given. 



The Polyzoa were associated by H. Milne-Edwards with the 

 Tunicata in the group Molluscoidea (Molluscoides 5 ), to which 

 the Brachiopoda were afterwards added by Huxley. 6 A know- 

 ledge of the development of the Tunicata has, however, shown 

 that these animals must be withdrawn from any association with 

 the other two groups ; while there is little real evidence that even 

 the Brachiopods have anything to do with the Polyzoa. 



Classification. The Polyzoa are divided into two sub- 

 classes : I, the ENTOPROCTA ; and II, the ECTOPROCTA/ Al- 

 though the character referred to by these terms is merely the 

 position of the anus with relation to the tentacles, 8 there can be 

 no doubt that the two groups differ widely from one another in 



1 Zoological Researches and Illustrations, Y. "On Polyzoa." Cork, 1830. 



2 "Symbolae Physicae," 1831, and Alh. Ak. Berlin, 1832, i. p. 377, etc. 



:t T. dt. p. 92. 4 Vol. i. 1880, Introduction, p. cxxxi. 



' J EMnicns dc Zoologic, 2nd cd. Aninuiux sans J'crtebrcs, 1843, pp. 238, 312. 

 Prof. A. Milne-Edwards has kindly written to me, informing me that he believes 

 this to have been the first occasion on which the term was thus used. 



6 Phil. Trans, vol. cxliii, 1853, p. 62. 



7 Nitsche, Zeitschr. v:iss. Zool. xx. 1870, p. 34. 



aims ; ivr6s, within ; ^*cT6s, without. 



