APPENDIX. 519 



for, from their catching their food in the same 

 manner as fish ; and this is rendered still more 

 probable, since the form of the mouth varies ac- 

 cording as they have or have not teeth. There is 

 however in the Whale tribe more variety in the 

 form of the head than of an}^ other part, as in the 

 Whalebone, Bottle-nose, and Spermaceti Whales ; 

 though in this last it appears to owe its shape, in 

 some sort, to the vast quantity of spermaceti 

 lodged there, and not to be formed merely for 

 the catching of its prey. From the mode of their 

 progressive motion they have not the connexion 

 between the head and body that is called the 

 neck, as that would have produced an inequality 

 inconvenient to progressive motion. 



The body behind the fins or shoulders dimi- 

 nishes gradually to the spreading of the tail ; but 

 the part beyond the opening of the vent is to be 

 considered as tail, although to appearance it is a 

 continuation of the body. The body itself is flat- 

 tened laterally, and I believe the back is much 

 sharper than the belly. 



The projecting part, or tail, contains the power 

 that produces progressive motion, and moves the 

 broad termination, the motion of which is similar 

 to that of an oar in sculling a boat : it supersedes 

 the necessity of posterior extremities, and allows 

 of the proper shape for swimming. 



The tail is flattened horizontally, which is con- 

 trary to that of fish, this position of tail giving the 

 direction to the animal in the progressive motion 

 of the body. 



