180 COMPARISONS OF STRUCTURE IN ANIMALS. 



to separate or attach themselves to the weeds; 

 this is done by the under part of their cheeks 

 or chin, which is also used for raising the body 

 when a new spot is wanted for the tail to 

 entwine afresh. Their eyes move independ- 

 ently of each other, as in the chameleon; this, 

 with the brilliant changeable irridescence about 

 the head, and its blue bands, forcibly remind 

 the obsei'ver of that animal.' " 



Thus, then, in the prehensile tail of this fish, 

 have we an organ of touch and an instrument 

 for grasping; a substitute, to a certain degree, 

 for the hand, and used by the animal for 

 moving itself while it looks out for prey. "We 

 may easily conceive that the vertebral of the 

 flexible elongated tail are modified so as to 

 admit of the necessary freedom of motion — and 

 that the arrangement of the muscles must be 

 very different from what it is in the ordinary 

 examples of the present class. In connexion 

 with this departure from the ordinary type of 

 structure, the habits and manners of the hippo- 

 campus are peculiar. It smms in a vertical 

 position, and very easily and gracefully, by 

 means of an undulating movement of the tail, 

 aided by the pectoral and dorsal fins; it clings 

 to objects for support, and has been observed 



