136 EVOLUTION, GENETICS, AND EUGENICS 



diagram by Marsh, and in this (Fig. 31) the reader may trace upward 

 from Orohippus to Equus the steady changes in fore and hind feet, 

 bones of the forearm, bones of the lower leg, and the grinding teeth 

 of upper and lower jaws. 



So definitely and clearly has the horse pedigree been worked out 

 that, according to Dendy, "the palaeontological evidence amounts to 

 a clear demonstration of the evolution of the horse from a five-toed 

 ancestor along the lines indicated above." 



For a long time the palaeontological series of the horse was un- 

 rivaled by other vertebrate types, but now we have almost equally 

 complete series for several other modern types, notably the camels 

 and the elephants. We shall present herewith accounts of the pedi- 

 gree of the camels by Professor Scott, and that of the elephants by 

 Professor Shull. And, to conclude the vertebrate pedigrees, we shall 

 present in the next chapter that of man as given by Professor Lull. 



In extenuation of the use of vertebrate material to the exclusion 

 of invertebrate, the present writer has only this to offer, that verte- 

 brate material is more intelligible to the non-biological reader and is 

 more in his own field of knowledge and interest. 



PEDIGREE OF THE CAMELS 1 

 W. B. SCOTT 



There remains one family of mammals with which it is necessary 

 to deal and that is the camel tribe. This family has two well-defined 

 subdivisions, the camels of the Old World and the llamas, guanacos, 

 etc., of South America. For a very long time, the family was entirely 

 confined to North America and did not reach its present homes until 

 the Pliocene epoch of the Tertiary period. The skeleton of a Patago- 

 nian guanaco may be taken as the starting point of our inquiry. In 

 this animal the third incisor and the canine are retained in the upper 

 jaw, all the incisors and the canine in the lower. The anterior two 

 grinding teeth have been lost and the others are moderately high- 

 crowned. The skull is broad and capacious behind, narrow and 

 tapering in front. The neck is long and its vertebrae very curiously 

 modified. The limbs are long and slender and have undergone nearly 

 the same modifications as in the horses; the ulna is greatly reduced, 

 interrupted in the middle and its separated portions are fused with the 

 radius. In the hind leg the shaft of the fibula has been completely 



'From W. B. Scott, The Theory of Evolution (copyright 1917). Used b> 

 special permission of the publishers, The Macmillan Company. 



