34 EVOLUTION 



respectively subjected. Similarly, all the different 

 breeds of dogs were supposed to have arisen owing to 

 the different habits which the various successors of the 

 first domesticated dogs acquired, small changes being 

 accumulated by inheritance in each successive genera- 

 tion. 



Turning now to species in a state of nature, the case 

 of the giraffe is one of those most often quoted. 

 Lamarck supposed a comparatively short - necked 

 ancestor of the giraffes to have taken up the habit of 

 browsing upon the leaves of trees, owing to the diffi- 

 culty of obtaining other food in an arid region. In 

 order to obtain their new food the animals were obliged 

 to be continually stretching upward, and the effort to 

 elongate their necks was attended with some small 

 measure of success in each individual. This increase, 

 being accumulated by inheritance in every succeeding 

 generation, ultimately led to the great stature exhibited 

 by the giraffes of the present day. 



The stilt -like legs of many wading birds were ascribed 

 by Lamarck to the result of the continued attempts of 

 ancestors which had shorter extremities to obtain their 

 food in shallow water without wetting their feathers. 

 The long-continued endeavours of these birds to stretch 

 and elongate their legs had the same effect as the 

 similar efforts made by the ancestors of the giraffes. 

 It has been suggested, however, by a critic of Lamarck's 

 position that such birds would be likely to eschew fish 

 dinners long before any notable increase in the length 

 of their legs was arrived at. 



If some of the above cases appear a little ludicrous, 



