THE AMPHIBIOUS CARNIVORA. 55 



able cavity corresponds with that of the body of the 

 vertebrae, and is filled with a reddish-looking jelly. 

 This curious structure, it will at once be seen, ad- 

 mits of far more extensive motion than is usual. 

 Again, the muscles of the spine undergo great and 

 corresponding modifications ; but on these we shall 

 not dwell longer than to remark that they are peculiar- 

 ly strong on all sides. When, then, the Seal wishes to 

 move forward, it bends underneath it the hinder part 

 of its spine, so making a kind of arch, and then fixing 

 this posterior portion, it suddenly straitens out the 

 whole bod} 7 in front ; and in a repetition of this move- 

 ment consists the very peculiar kind of jerking leap 

 for which these amphibia are so famous. This is so 

 singular that it has been dwelt upon, and described 

 with sufficient accuracy, by several observers who 

 knew nothing of their comparative anatomy. To 

 give one example. " Their mode of propelling 

 themselves," says Weddell, "is by drawing their 

 hinder flippers forwards, thereby shortening their 

 body, and then projecting themselves from the 

 tail."* When, again, they wish to ascend an ice- 



* The account in the text is more satisfactory than the follow- 

 ing, whilst it is, at the same time, corroborated by it. * The 

 Common Seal in the Zoological Gardens, when on the land, 

 scarcely uses its feet in walking, but only the abdominal muscles, 

 jerking itself forward by a series of convulsive motion*. It only 

 used its fore-feet to assist in balancing itself, and when it turned 

 on one side, it expanded its hinder feet, which are generally con- 

 tracted and held together, with the depressed forked tail between 

 theii base," J, E. Gray, Annals of Nat. Hist. ; Sept. 1838, 

 p. 78. 



