186 HALF AN HOUR WITH SHELL-FISH. 



There is the head, with eyes, mouth, &c., and the 

 posterior part, containing the internal organs. The 

 mouth is yery peculiar for its horny jaws, which are 

 hardened by carbonate of lime diffused through the 

 tissues, and are not unlike those of a parrot in 

 appearance. The tongue, also, is no less striking, 

 being armed with recurved spines, so that the 

 mechanism for getting rid of prey is pretty perfect. 

 The mouth leads into an internal muscular cavity, 

 for the further trituration of the food. Not less 

 curious are the eyes of the cuttle-fish, which have 

 long been a puzzle to naturalists and opticians, 

 although they seem to approach, in structure, the 

 " Coddrington lens " more than anything else. Sir 

 David Brewster and other learned men have devoted 

 their attention specially to the optical principles on 

 which the eyes of this creature are based. Another 

 curious and remarkable contrivance for this animal 

 is full of singular adaptations is the means of respi- 

 ration and progression. Both these important func- 

 tions are achieved by a very simple method. Just 

 below the neck of the cuttle-fish, outside, may be 

 noticed two slits, leading into what are called the 

 " branchial chambers ;" that is, the gill- or breathing- 

 chambers, corresponding to the lungs of the higher 

 animals. In the ordinary cuttle-fish there are 

 placed two gills ; in the Nautilus family four. The 

 sea-water is admitted by the external apertures to 

 these gills, and supplies them with the air that 

 happens to be mechanically mixed up with it. After 



