ORIGIN OF THE DIVERSE FORMS OF ANIMAL LIFE 853 



beneath the skin in the position of the hind limbs. Teeth 

 are present in the jaws of the whalebone whales, but they 

 never appear above the surface, and 

 the young of the ruminants have 

 buried in the gums minute upper 

 incisors, though they do not de- 

 velop into functional teeth in the 

 adults. The vermiform appendix, 

 occurring in man and the anthro- 

 poid apes, is of no use, but in their 

 ancestors it may have played an 

 important part in digestion, as the 

 corresponding portion of the ali- 

 mentary canal does yet in the rab- 

 bit, groundhog, and other forms. 

 The splint bone, about ten inches 

 long on either side of the lower part 

 of the horses' limb, serves no useful 

 purpose now. All of these useless 

 structures clearly indicate that they 

 were of larger size in the far-off an- 

 cestors in whom their presence was 

 of great use. 



Still further testimony, favoring 

 a belief in evolution, is given by the 

 study of Embryology which deals 

 with the development of the young 

 from the egg. In very young stages the higher verte- 

 brates are seen to resemble the adult forms of some of the 

 lower animals. The chick, when taken from an egg 

 incubated for three days, is found to have gill slits and 



FIG. 395. Skeleton of the 

 fore limb of the horse. 

 sc, shoulder blade ; h, hu- 

 merus ; r, radius ; ua, 

 ulna; m 3 , third metacar- 

 pal; m 4 , splint bone or 

 fourth metacarpal ; p t 

 phalanges. From Davi- 

 son's " Mammalian Anat- 

 omy." 



