S0 THE NEW EVOLUTION "^^"^ 



an illustration of continuity of life from parent to 

 child coupled with abrupt and striking discontinuity 

 in form, and also in mental traits, let us consider 

 the dogs. 



According to the best authorities, all of the nearly 

 two hundred different breeds of domesticated dogs 

 are descended -rom a single type of ancestor, which 

 was a wolf or wolves closely resembling our native 

 wolf but with slightly different teeth. The domestic 

 dogs may be grouped, following Gibson, into wolf- 

 dogs, greyhounds, spaniels, hounds, mastiffs and 

 terriers. 



Some of the wolf-dogs, as for instance the dogs of 

 the Esquimaux and of the Kamchadales, show a more 

 or less close resemblance to wolves and are said to 

 interbreed with them, while others, as the collies, 

 police-dogs, sheep-dogs, Newfoundlands and St. Ber- 

 nards, are much less wolf-like. But the wolf-dogs 

 may be arranged in a fairly continuous series from 

 the most to the least wolf-like. 



This series of dog forms is parallel to many of the 

 evolutionary lines which are seen in the geological 

 history of the mammals, as for instance in the horses, 

 camels and hyaenas. It is a series of types which 

 differ only slightly from each other running, with 

 many side branches and ramifications, between two 

 extremes which are widely different. 



Of the other breeds of dogs we may select the grey- 

 hounds, hounds, bull-dogs and pugs — the last two 

 from the mastiff stock — as representative types known 

 to everyone. 



