INTRODUCTION. 



CXI 



(Woodcut, fig. xlv., 3, compared with 1 and 2) and the 

 foot-bearing Polyzoa. In the former the line of gills is 

 interrupted behind the foot; and so it is in Rhabdopleura^ . 

 The arm of the latter is also strictly comparable with the 

 gill-plume of the Gasteropod. 



The tentaclesj then, of the Polyzoa are the homologue 

 of the Molluscan gills ; in some of their modifications 



Fig. xlv. 



1. Phylactolcemafoiis Polyzoon. 2. Rliabdopleura. 3. Young Cyclas. 

 M. Mouth. A. Anus. F. Foot. G. Gill- ten tacle.s. ng. Nei-Te-ganglion . 



* See Ear Lankester, " Notes on Embryology," Quart. Journ. Micr. Sc. 

 xvii. (n. s.) p. 424; "Affinities of Rhahdopleura," ibid. xiv. (n. s.) p. 77: 

 Huxley, ' Classification of Animals,' Brachiopoda : Hancock, " Anatomy of 

 Freshwater Polyzoa," Ann. N. H. 1850. 



