74 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



suppressed; the upper end fuses with the tibia, while the lower remains 

 as a small separate bone, wedged in between the tibia and the heel- 

 bone. The feet are very long and slender, with two toes in each; the 



Fig. 3. — Four stages in the evolution of the cameline skull. A, Protylopiis 

 Upper Eocene; B, Poebrotheriiim, Lower Eocene; C, Procamelus, Upper Miocene, 

 Z>, guanaco, Recent. {From Scott.) 



long bones of the foot are co-ossified to form a '^ cannon-bone, " the 

 very young skeleton showing that this co-ossification does actually take 

 place. The toes proper are free, giving the "cloven hoof," but the 

 hoofs are very small and the weight is carried upon a soft, thick pad. 



