SEPIA OFFICINALIS. 



one flexible and transparent, similar to horn, and smooth on 

 the surface. The third layer is destitute of lustre, and in hard- 

 ness and structure resembles mother-of-pearl shells. The 

 term bone has been improperly applied to this complicated 

 plate, for this substance in composition is exactly similar to 

 shell, and consists of various membranes, hardened by carbo- 

 nate of lime, without the smallest mixture of phosphate. The 

 cuttle-bone is formed in the same manner as other shells, by 

 the continued addition of calcareous laminee secreted by that 

 side of the containing capsule which is interposed between the 

 shell and the abdominal viscera, and these layers, being succes- 

 sively added to the ventral surface of the shell, thus gradually 

 increase its bulk as the cuttle-fish advances to maturity. 

 Neither in the mode of its growth nor in its texture, therefore, 

 does the os sepice resemble bone, properly so called ; it receives 

 neither vessels nor nerves, but is in all respects a dormal secre- 

 tion embedded in the mantle and formed in the same manner 

 as the dorsal plate of the slug. 



In all the CEPHALOPODA, with the exception of the Nautilus 

 Pompilius, there is an orifice in the immediate vicinity of the 

 anus, through which a colored secretion, generally of a deep 

 brown or intense black color, can be poured in astonishing 

 abundance, and, becoming rapidly diffused through the sur- 

 rounding water, thus provides a means of defence ; for no 

 sooner does danger threaten, or a foe appear in the vicinity of 

 the cuttle-fish, than this ink is copiously ejected, and the ele- 

 ment around rendered so opaque and cloudy that the Cepha- 

 lopod remains completely concealed from its pursuer, and not 

 unfrequently insures its escape by this simple artifice. The 

 organ wherein the inky secretion is elaborated is a capacious 

 pouch lodged near the bottom of the visceral sac. On open- 

 ing it and carefully washing away by copious ablution the 

 ink within, the cavity of the ink-bag is seen to be filled up 

 with a spongy cellulosity, wherein the blacking material had 

 been entangled ; and from this cellular chamber a duct leads 

 to the outward orifice, through which the dark secretion is 

 ejected at the will of the animal, and squirted from the ex- 

 tremity of the funnel. 



The most remarkable species of the genus is the SEPIA 

 OFFICINALIS, 'which is distinguished from the others by its 

 smooth skin. It inhabits the British seas, and although sel- 

 dom taken, its " bone " is cast ashore on different parts of the 





