152 NATURAL THEOLOaY. 



supposition of the difference being produced by action or use, 

 A more prominent contour, or a wider gap, might be resolv* 

 ed into the effect of continued efforts, on the part of the 

 species, to thrust out the mouth or open it to the stretch. 

 But by what course of action, or exercise, or endeavor, shall 

 we get rid of the lips, the gums, the teeth, and acquire in 

 the place of them pincers of horn? By what habit shall 

 we so completely change, not only the shape of the part, but 

 the substance of which it is composed ? The truth is, if wo 

 had seen no other than the mouths of quadrupeds, we should 

 have thought no other could have been formed : little could 

 we have supposed that all the purposes of a mouth furnish- 

 ed with hps and armed with teeth could be answered by an 

 instrument which had none of these — could be supplied, and 

 that with many additional advantages, by the hardness and 

 sharpness and figure of the bills of birds. Every thing about 

 the animal mouth is mechanical. The teeth of fish have 

 their points turned backward, like the teeth of a wool or 

 cotton card. The teeth of lobsters work one against another, 

 Hke the sides of a pair of shears. In many insects, the mouth 

 is converted into a pump or sucker, fitted at the end some- 

 times with a wimble, sometimes with a forceps ; by which 

 double provision, namely, of the tube and the penetratmg 

 form of the pomt, the insect first bores through the integu- 

 ments of its prey, and then extracts the juices. And what 

 is most extraordinary of all, one sort of mouth, as the occa- 

 sion requires, shall be changed into another sort. The cat- 

 erpillar could not live without teeth ; in several species, the 

 butterfly formed from it could not use them. The old teeth, 

 therefore, are cast off with the exuviae of the grub ; a new 

 and totally difierent apparatus assumes their place in tho 

 fly. Amid these novelties of form, we sometimes forget that 

 it is all the while the animal's mouth — that whether it be 

 hps, or teeth, or bill, or beak, or shears, or pump, it is the 

 same part diversified ; and it is also remarkable, that under 

 all the varieties of configuration with which we are acquaii>*' 



