VII 



MOL L USCA—RESPIRA TOR Y ORGANS 



85 



bilateral symmetry of the body, such as the Lamdlihranrlua, the 

 Cephalopoda, and-a point of great importance-also in the primitive 



Fis ure^^~D ^ucl P P 71 '°^ ^'""' ^""^ Lankester). A, Chiton; B, Sepia; C, 



vesseT W, .' 5 T^ • ,' ^^^^<i'°^- /'. Longitudinal branchial muscle ; „M; atlLre, t bran.'hia 



Gastropoda, the Zeugohmnchia. In the latter, however, the left ctenidium 

 was originally the right and vice vend, but this will be dealt with more 

 in detail later. 



