356 



MOLLUSC A. 



by a fin, is shaped like a shield, the broad end of which 

 bears a narrowed head, with eight short and two long 

 sucker-bearing arras. Besides the diffuse pigment cells, 

 there are bands across the " back." The large eyes, the 

 parrot-beak-like jaws protruding from the mouth, the spout- 

 like funnel on the neck, and the mantle cavity, are con- 

 spicuous. Beside the eyes are the small olfactory pits ; 



within the mantle cavity lie 

 the anus and the openings 

 of the nephridia and genital 

 duct. 



The true orientation of the 

 different regions in Sepia is 

 not obvious. If the "arms " 

 surrounding the mouth be 

 divided portions of the an- 

 terior part of the " foot," the 

 ventral surface is that on 

 which the animal rests when 

 we make it stand on its 

 head. We can fancy how 

 the " foot " of a snail might 

 grow forward and surround 

 the mouth, so as to bring 

 that into the middle of the 

 sole. Then the visceral 

 mass has been elongated in 

 an oblique dorso-posterior 

 direction, so that the tip of 

 the shield, directed forward 

 when the cuttle jerks itself 

 . away from us, represents in 

 anatomical strictness the dorsal surface tilted backwards. 

 (As above noticed, the animal may also swim with foot and 

 mouth in front.) The side of lighter colour, marked by the 

 mantle cavity and the siphon or funnel, is posterior and 

 slightly ventral ; the banded and more convex side, on which 

 the cerebral ganglia lie in the head region, and on which 

 the shell lies concealed in the visceral region, is anterior 

 and slightly dorsal. 



Skin. — There are numerous actively changeful pigment 



Fig. 155. 



-External Appearance of a 

 cuttlefish. 



