354 



MARINE INVERTEBRATES 



in most nudibranchs is extremely large and completely surrounds the 

 stomach, in Dendronotus also extends into these dorsal cerata, so that 

 they may have some sort of digestive function. 



JJendruitotitK ;/</>. v 



GENUS JEolis 



IE. paplllosa. This is probably the commonest nudibranch upon 

 the North Atlantic coast, and it occurs as frequently in European 

 waters. It may readily be found clinging to stones, algae, the piling of 

 wharves, eel-grass, etc., in bays or in rocky tide-pools. The color is 

 yellowish-gray to orange, with purplish or olive 

 spots. The cerata are very numerous, and cover the 

 dorsal portion of the animal save for an open space 

 along the middle of the back. There are two sets of 

 tentacles, the two dorsal and the two simple labial 

 tentacles. The foot tapers behind to a sharp point, 

 and is truncate in front. As in Dendronotus, the 

 liver is diffused into the cerata, which in JEolis are 

 simple tubular processes without the branching 

 character of those of the former. Both species lay 

 their eggs in a gelatinous, bobbin-like cord, which 

 is hung in festoons over rocks or upon zoophytes, or 

 at times they wind the cord in a coil upon the sur- 

 faces of stones. When the young first hatch out, 

 they are provided with a glassy nautiloid shell, a fact 

 which would indicate that at some remote period they 

 were, like most mollusks, provided with a shell. JEolis swims in an in- 

 verted position, and is at times exceedingly active. It is very variable in 

 coloring and in the number of cerata. 



GENUS Doris 



D. bilamellata. In Doris we find a quite different type of nudi- 

 branch from that presented by the two genera Dendronotus and JEolis. 

 In one there were numerous branched cerata or dorsal papillae, in the 

 other many plain cerata, and in neither case were thei-e any specialized 



jEolis paplllosa. 



