EXTE:^rSIOXS of DARWIXISM 291 



striking cases are those of the Mesozoic reptiles and the early 

 Tertiary ungulate mammals, which both increased to such an 

 enormous bulk, yet retained throughout an almost ludicrously 

 small brain, as described in the last chapter. The same was 

 the case to a somewhat less extent with the carnivorous mam- 

 mals, the Creodonta and Sparassodonta of the early Tertiaries 

 both of the eastern and western hemispheres. These were 

 sometimes as large as lions or bears, and had equally well de- 

 veloped canine teeth, but very small brains; and they all died 

 out in Eocene or early Miocene times, giving way to small an- 

 cestral forms of our modern carnivores, which then increased 

 in size and developed larger brains, culminating in the highly 

 intelligent fox and dog, cat and leopard, of our own day. 



Yet another singular feature of some of the more highly 

 developed vertebrates is the partial or total loss of teeth. This 

 is well shown in the camels, which have only a pair uf in- 

 cisors in the upper jaw; while the whole vast family of the 

 deer, cattle, and sheep have a completely toothless pad in the 

 front of the upper jaws. This is apparently better adapted 

 for rapid browsing of grass and low herbage — whieli is stored 

 up in the 23aunch for rumination when at rest; and the ab- 

 sence of teeth as a defence is compensated by the possession 

 of horns in a great variety of form and structure. 



Even more remarkable is the total loss of teeth bv modern 

 birds, although the early types of birds possessed them. The 

 bill, however, is often a very effective piercing or tearing 

 weapon ; and their strongly grasping claws and hooked bill 

 render the birds of prey almost as powerful and d instructive 

 as the smaller members of the cat-tribe. This partial or total 

 disappearance of the teeth has no doubt been helped on l)y the 

 same principle which led to the persistent increase of useless 

 appendages till checked by natural selection or till it led to 

 the extinction of the entire race. 



