y 



242 THE THEORIES OF EVOLUTION 



amount of light on the opposite side, the eyes of 

 snakes which enable those animals to see everything 

 above them while they glide on the ground, the broad- 

 ening of the body in herbivorous mammals, due to 

 their attitudes, the claws, retractile and otherwise, of 

 birds of prey, the special conformation of the ostrich 

 and of the kangaroo. He also gives the classical ex- 

 ample of the giraffe. "The long neck and the form 

 of the giraffe offer a curious case. We know that the 

 giraffe is the tallest of all animals. It inhabits the 

 centre of Africa, living in those localities where 

 the earth is nearly always dry and without herbage. 

 It is obliged to browse on the foliage of trees, and this 

 leads to its stretching its neck continually upwards. 

 As a result of this habit, carried on for a long time, in 

 all the individuals of the race, the anterior limbs have 

 become longer than the posterior, and the neck has also 

 lengthened, so that the giraffe without rising on its 

 hind legs stretches up its neck and can reach to the 

 height of six metres." 7 



From all those examples Lamarck deducts his first 

 law: "In every animal, that has not passed beyond 

 the term of its development, the frequent and sus- 

 tained use of any organ strengthens it, develops it, 

 increases its size, and gives it strength proportionate 

 to the length of time of its employment. On the 



7 Vol. I, pp. 254-255. 



