256 ON THE CLASSES OF THE 



toise, may be detected lining that of S. Octopus. The 

 spiral stomach of the Cephalopoda, its sudden dilatation, 

 and its lining of longitudinal folds, may likewise be traced 

 to the tortoise. The gizzard is a character common to 

 birds and the Cephalopoda, and this may be accounted 

 for by considering the near affinity which exists between 

 tortoises and birds. In S. Loligo however, that is, one 

 of the nearest of the Cephalopoda to the Vertebrata, this 

 gizzard is smaller and more slender than in S. Octopus. 

 The probability therefore is, that it is a structure by which 

 these animals are to be referred rather to their own type 

 than to any truly vertebrated animal. Nevertheless the 

 whole of the alimentary organs of the Cephalopoda must be 

 reckoned extremely analogous to those of reptiles, and 

 particularly to those of the tortoises. The two-lobed liver 

 with its situation, nay, even the two hepatic canals are 

 all visible in a Chelonian reptile, in which, as well as in 

 the Cephalopoda, the peritoneum, which comprehends all 

 the viscera, is divided into several subdivisions in front, co- 

 vering the liver and forming a sort of diaphragm. This 

 peritoneum indeed is perfectly analogous to that of the 

 vertebrated animals, and differs from that of the Mollusca 

 in that it does not cover the brain nor the mass of the 

 mouth in general. It is true that the rectum of the Cepha- 

 lopoda opens in front of the neck, and it may be asked, 

 What similar position of this organ is there among rep- 

 tiles ? But the proper method of putting the question is, 

 What similar position can be found among the Verte- 

 brata ? since, in fact, it is a character of the Mollusca 

 that the situation of the rectum should be subject to no 

 general rule. 



Cuvier says of the tortoises, " Ces animaux se distin- 



