COMPARATIVE AI^ATOMr. 15S 



The rest of the iins, therefore, so far as respects motion, seem 

 to be merely subsidiary to this. In their mechanical use. 

 the anal fin may be reckoned the keel ; the ventral fins, out- 

 riggers ; the pectoral muscles, the oars : and if there be any 

 similitude between these parts of a boat and a fish, observe, 

 that it is not the resemblance of imitation, but the likeness 

 which arises from applying similar mechanical means to tha 

 same purpose. 



We have seen that the tail in the fish is the great instru- 

 ment of motion. Now, in cetaceous or warm-blooded fish, 

 which are obliged to rise every two or three minutes to the 

 surface to take breath, the tail, unlike what it is in other 

 fish, is horizontal ; its stroke, consequently, perpendicular to 

 the horizon, which is the right direction for sending the fish 

 to the top, or carrying it down to the bottom. 



E-egarding animals in their instruments of motion, we 

 have only followed the comparison through the first great 

 division of animals into beasts, birds, and fish. If it were 

 our intention to pursue the consideration farther, I should 

 take in that generic distinction among birds, the web-foot 

 of water-fowL It is an instance which may be pointed out 

 to a child. The utility of the web to water-fowl, the inutil- 

 ity to land-fowl, are so obvious, that it seems impossible to 

 notice the difference wdthout acknowledging the design. I 

 am at a loss to know how those who deny the agency of an 

 intelligent Creator dispose of this example. There is nothing 

 in the action of swimming, as carried on by a bird upon the 

 surface of the water, that should generate a membrane be- 

 tween the toes. As to that membrane, it is an exercise of 

 constant resistance. The only supposition I can think of is, 

 that all birds have been originally water-fowl and web- 

 footed ; that sparrows, hawks, hnnets, etc., which frequent 

 the land, have, in process of time, and in the course of many 

 generations, had this part worn aw^ay by treading upon 

 hard ground. To such evasive assumptions must atheism 

 always have recourse I And after all, it confesses that the 



