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 tentacles, then, of the Polyzoa are the homologue 

 of the Molluscan gills; in some of their modifications 



Fig. xhr. 



1 I'hylactoltfinatou* Polyeoon. 2. Rhabdopleura. 3. Young Cyclaa. 

 M. Mouth. A. Anu*. F. Foot. G. Gill-tentacles, ng. Nerre-ganglion. 



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

 rrii. (n. .) p. 424 ; "Affinities of Rhabdopleura," ibid. xiv. (n. .) p. 77: 

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

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



