Orr's Views 



of the environment in determining or modifying 

 organisms. 



The similarity of the views of Orr and 

 Lamarck is best seen by comparing their re- 

 spective explanations of the long neck of the 

 giraffe. Lamarck thought that this was the 

 direct result of continual stretching. The animal 

 continually strains its neck in the search for food, 

 hence it grows longer as the individual grows 

 older, and this elongated neck has been trans- 

 mitted to the offspring. Orr writes, on page 164 

 of his Development and Heredity : " The giraffe 

 seems to present the most remarkable illustration 

 of the lengthening of the bones as the result of 

 the frequent repetition of such shocks. As is 

 well known, this animal feeds on the foliage of 

 trees. From the earliest youth of the species, 

 and the earliest youth of each individual, it must 

 have been stretching upwards for food, and, as is 

 the custom of such quadrupeds, it must have 

 constantly raised itself off its forefeet, and, as it 

 dropped, must have received a shock that made 

 itself felt from the hoofs through the legs and 

 vertical neck to the head. In the hind legs the 

 shock would not be felt. It is impossible to 

 imagine that an animal which, during the greater 

 part of every day of its life (both its individual 

 and racial life), performed motions so uniform 

 and constant, would not be peculiarly specialised 

 as a result. The forces acting upon such an 



B 17 



