THE CEPHALOPODA 



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female, but only sixty in the male. These tentacles have laminated 

 but not ciliated surfaces ; they are adhesive and prehensile, and 

 are retractile within special tentacular sheaths. When the animal 

 is extended they radiate outwards from the mouth. In the female 

 there are three tentaculiferous lobes in immediate contact with the 

 buccal aperture (Fig. 255, c, d) : these are the right and left and the 

 ventral interior lobes. The last named (which is absent in the 

 male) bears a laminated organ, supposed to be olfactory in function 

 and known as Owen's organ, in the middle of its free border (Fig. 

 255, n), and fourteen tentacles on each moiety of the lobe. The 



Fio. 254. 



Tremoctojms velifer, Verany, viewed from the dorsal side, showing the four dorsal arms joined 

 together by a membrane. (After Verany.) 



right and left interior lobes bear twelve tentacles apiece. The 

 muscular mass of the foot forms a broad ring round the three interior 

 lobes, and is particularly thick and strong in the dorsal region (Fig. 

 255, g), where it is modified to form a hood which protects the whole 

 animal when it is retracted within its shell. On the external face 

 of the hood is a concavity in which the spire of the shell is lodged. 

 The tentacles borne on this ring are called " digital," and are 

 larger than the " labial " tentacles borne on the three interior lobes. 

 The digital tentacles are nineteen in number on each side in the 

 female, and are disposed more or less regularly in three unequal 

 rows. It is only the dorsal pair of tentacles that belongs to that 

 part of the muscular ring which forms the hood, the last-named 



