STRUCTURE, ETC., OF OERATA OF NUDIBRANOHS. 51 



part of the body. They contain large branched hepatic 

 diverticula, and are therefore hepato-cerata. 



Transverse sections of Do to coronata show the relatively 

 very large size of the hepato-cerata (fig. 2B), and the manner 

 in which they are occupied by numerous branches of the large 

 hepatic cseca ; ten or a dozen branches may often be found 

 lying in one section. In fact, in this form, there is far more of 

 the liver in the cerata than in the body proper. The median 

 portion of the liver is reduced to a small tube flattened dorso- 

 ventrally, which lies along the under surface of the large ovo- 

 testis (see figs. 23 and 27, m. L), and gives off at intervals lateral 

 branches, which run up the sides of the ovo-testis (figs. 25 and 

 26, h. c.') to enter the cerata, and there expand into the large 

 branched caeca. The difference, then, between this state of 

 affairs, where the part of the liver in the body is little more 

 than a duct leading from the hepato-cerata to the stomach, and 

 that seen in Ancula, Tritonia, and Dendronotus, where 

 the liver is wholly in the body, and the parieto-cerata are 

 merely processes of the mesoderm and ectoderm of the integu- 

 ment, is very great, and affords sufficient ground, I think, for 

 the separation of the cerata into two categories. 



EoLis. 



For my present purpose it is convenient to use the term 

 Eolis in its older, wide sense, as employed for example by 

 Alder and Hancock, and as including the modern genera 

 Facelina, Flabellina, Coryphella, Galvina, &c. In 

 these forms we have much the same condition as in Do to. 

 There are no true branchiae, rhinophores are present, and there 

 are also large coloured hepato-cerata arranged along the back 

 (PI. X, fig. 29), and constituting the most conspicuous part of 

 the animal. 



The hepatic diverticula in the cerata are either simple or not 

 so much branched as in Do to, and are not caecal, but com- 

 municate indirectly witii the exterior at their apices. The 

 hepato-cerata also contain at their apices cnidophorous sacs 



