778 



CONCLUSION 



lines. It is as if the vertebrate organization produced time after time 

 slightly different variations on a series of themes. Thus animals that 

 feed on fishes acquire long jaws and numerous teeth. We have examples 

 of these characteristics among the fishes themselves (garpike, Belone) 



Fig. 514. Skeleton of the hand in various mole-like mammals. 



a, Talpa; b, Chrysochloris; c, Notoryctes (palmar view); d, dorsal 



view of the same. r. radius; rs. radial sesamoid; u. ulna. (From Lull, 



Organic Evolution, copyright 1917, 1929 by The Macmillan Company 



and used with their permission.) 



and in the crocodiles, phytosaurs, ichthyosaurs, plesiosaurs, birds, and 

 mammals. Perhaps even more remarkable are the 'duck-bills' of 

 animals that sift small invertebrates from mud. There is a distinct 

 similarity in the structures used for this purpose by Polyodon, the 

 ducks themselves, and the platypus. One could continue with endless 

 examples of the same sort, for instance, the large mouth of insect- 

 eating animals — the frogs, swallows, swifts, and bats. The five sorts 

 of ant-eater found among mammals provide another remarkable 

 example of this 'convergence' ; all have an elongated snout, long sticky 



