CEPHALOPODA. 307 



situated near tlie bottom of the sac, which, by means of vari- 

 ous arteries, distributes the blood to every part of the body. 



Respiration is effected by the water which flows into the 

 sac and issues through the funnel. It appears that it can even 

 penetrate into two cavities of the peritoneum, traversed by 

 the vena cava in their passage to the branchiae, and act upon 

 the venous blood by means of a glandular apparatus attached 

 to those veins. 



Between the base of the feet we find the mouth armed with 

 two stout horny jaws resembling the beak of a parrot. 



Between the jaws is a tongue bristling with horny points ; 

 the oesophagus swells into a crop, and then communicates with 

 a gizzard as fleshy as that of a Bird, to which succeeds a third 

 membranous and spiral stomach, which receives the bile from 

 the two ducts of the very large liver. The intestine is sim- 

 ple and short. The rectum terminates in the funnel. 



These animals are remarkable for a peculiar and intensely 

 black excretion, with which they darken the surrounding 

 water when they wish to conceal themselves. It is produced 

 by a gland, and held in reserve by a sac, variously situated, 

 according to the species. 



Their brain, which is contained in a cartilaginous cavity of 

 the head, gives off a cord on each side which produces a large 

 ganglion in each orbit, whence are derived innumerable optic 

 filaments ; the eye consists of several membranes, and is co- 

 vered by the skin which becomes diaphanous in that particular 

 spot, sometimes forming folds which supply the want of eye- 

 lids. The ear is merely a slight cavity, on each side near the 

 brain, without semicircular canals or an external Meatus, where 

 a membranous sac is suspended which contains a little stone. 



The skin of these animals, of the Octopi particularly, 

 changes colour in places, by spots, with a rapidity which 

 greatly surpasses that of the Chameleon(l). 



The sexes are separated. The ovary of the female is in the 



(1) See Carus, Nov. Act. Nat. Cur., XII, part f, p. 320, and Satigiovanni, Ann. 

 des Sc. Nat. XVI, p. 308. 



