12 



COMFA RA TIVE A NA TOMY 



CHAP. 



at its anterior end. No jaws. The anus almost always dorsal. Except in the 

 Stcgaiwbranchia, the disappearance of the mantle and its cavity is accompanied bj^ 

 the disappearance of the single ctenidiiim of the Tectibranehia. 



Section 1. Steganobranchia. — With mantle, cavity, and ctenidium to the right ; 

 with a shell and [)ara podia. Fam. Oxynoidea {Oxynoe, Lobiger). 



Section 2. Cirrobranchia. — Leaf- or club-shaped processes found laterally on the 

 back. Fam. Hermseidse, Phyllobranchidse. 



Section 3. Pterobranchia. — The sides of the body produced into lobes, in 

 which the branches of the glands of the mid -gut spread out. Fam. Elysiadae, 

 Placobranchidse. 



Section 4. Abranchia. — Neither ctenidium, nor dorsal appendages, nor leaf-like 

 lateral expansions of the body. Respiration through the skin. The body is almost 

 like that of a Planarian. Fam. Limapontiidse. 



Sub-Order 3. Nudibranchia. 



Without mantle fold, shell, or ctenidium. Jaws almost always found. Radula 



A. // c 



Fio. IS.— Aeolis ruflbranchialis (right asppct, after Alder ami Hancock), a, Eye : h, oral 

 tentacle ; c, cephalic tentacle ; d, anus ; e, genital aperture ; /, dorsal respiratory appendages 

 (cerata). 



generally well developed, with teeth which fall off and are lost. Adaptive gills 

 very variously developed, Init occasionally wanting. 



10 ^ 



2 6 J 



Fin. 19. — Phylllrhoe bucephalum (lateral aspect, after Souleyet, luoditied). 1, Tentacle ; 

 2, cerebral gangli(jn ; 3, stoniach ; 4 and 12, intestinal ca-ca (forming the digestive gland) ; 

 5 ventricle ; 6, auricle ; 7, pericardial aperture of the kidney ; S kidney ; 9, external aperture of 

 the same (on the right side) ; 10, anus (on the right side) ; 11, liermaphrodite glands, the ducts not 

 drawn ; 13, genital apertures ; 14, buccal ganglion ; 15, salivary glands. 



Section 1. Holohepatica. — One large unbranched hepatic gland (liver). Fam. 



