286 THE CEPHALOPODA 
body reduced (Fig. 22, E). This is the result of the displacement of 
the foot, whose lateral borders surround the head and are joined 
together in front of the mouth. In consequence of this shortening 
of the antero-posterior axis, the two extremities of the digestive 
canal are closely approximated, 
and the pallial cavity opens im- 
mediately behind the head (Fig. 
252, m, a). 
The head is highly developed, 
but has hardly any other ap- 
pendages than those formed by 
the edges of the foot which 
Fia. 252. 
Diagram of the structure of a Cephalopod, 
as seen from the left side in its proper mor- 
phological position. a, anus; ar, arms; ce, 
central nervous system, with eye; coe, 
coelom ; fu, funnel; g, gill; go, gonad; h, Fic. 253. 
Pe ornie one won ae. ee months Taonius suhmii, Lankester, ventral 
eaiGardial erinee Pigigtonndan > TP, aspect. e, pedunculated eye; fi, fin; m, 
P ‘ eas Rs x mouth ; ¢, tentaculararm. (After Hoyle.) 
embrace it. Certain Oigopsida, however, e.g. Taonius suhmii, Ray 
Lankester (Fig. 253), and the embryos of an allied form known 
as Grenacher’s embryo (Fig. 119, D) and of Loligo peali, have very 
prominent pedunculated eyes. On the other hand, Nautilus, whose 
eyes are also somewhat prominent, has in addition two ciliated 
tentacles on either side of the head, one in front of and the other 
behind the eye (Figs. 255, 1,4; 293, a.o.t, p.o.t). 
The foot forms a crown of appendages surrounding the mouth: 
the edges of this crown are not deeply divided in Nautilus, but 
are much more so in the Dibranchia. In Nwutilus the circumoral 
pedal crown is divided into lobes each of which bears a group of 
tentacles, the total number of tentacles being about ninety in the 
