332 MOLLUSCS. 



retreat from an enemy. Its food includes fish, other 

 molluscs, and crabs. In spring the female attaches her 

 encapsuled eggs to sea- weeds and other objects, and often 

 comes fatally near the shore in so doing. The " cuttles " 

 are caught for food and bait. The " cuttle-bone " and the 

 pigment of the ink-bag are sometimes utilised. 



External Appearance. — A large Sepia measures about ten 

 inches in length and four or five in breadth ; the body, 

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

 which bears a narrower head, with eight short and two long 

 sucker-bearing arms. Besides the diffuse pigment-cells, 

 there are zebra-like bands across the " back," and the living 

 animal is certainly beautiful. The large eyes, the parrot- 

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

 funnel on the neck, and the mantle-cavity are conspicuous. 



The true orientation of the different regions in Sepia is not 

 obvious. If the " arms " surrounding the mouth be divided 

 portions of the anterior part of the " foot," the ventral sur- 

 face 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 direc- 

 tion, 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. 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. 



The Skin is remarkably beautiful, because of numerous 

 actively changeful pigment-cells or chromatophores, each of 

 which is expanded or contracted according to the state of 

 fine muscle-fibres which extend all round in radial directions. 

 Girod insists on calling these connective fibres, and perhaps 

 they are illustrations of a merging of these two kinds of 

 tissue. It is probable that these chromatophore cells have 

 some protoplasmic spontaneity of their own, but the con- 

 trolling fibres seem to be affected by nervous impulses from 

 the central ganglia. As the cells contract or dilate the colours 



