PHYLUM MOLLUSCA 



779 



and other soft parts about the head. Altogether there are forty- 

 two tentacles of the outer series, including four ophthalmic tentacles, 

 one situated on the oral and another on the aboral side of each 

 eye. The latter (ophthalmic) differ from the rest in being highly 



Fig. 676.— Nautilus macromplialus, adhering to the sub.stiatum in a vertical position by 

 means of its tentacles, e. eye ; h. hood ; n. ■lu. nuchal membrane detached from coil of shell ; 

 0. (. ophthalmic tentacles ; sft. shell ; w. /'. wing of funnel. (After Willey.) 



sensitive, ciliated, and with the ridges on the inner side produced 

 into lamellae. The tentacles of the inner series differ strikingly in 

 number and arrangement in the two sexes. In the female there 

 are two inner lateral lobes, right and left, quite symmetrically 

 developed, each bearing twelve tentacles, and an inner posterior 



