224 Evolution and Adaptation 



on a tree become elongated in consequence of becoming 

 stretched, hence has arisen the foot with the long toes char- 

 acteristic of arboreal birds. 



Shore-birds, " which do not care to swim," but must 

 approach the water in order to obtain food, will be in danger 

 of sinking into the mud, "but, wishing to act so that their 

 body shall not fall into the liquid, they will contract the habit 

 of extending and lengthening their legs." Hence have arisen 

 the stiltlike legs of shore-birds. 



These ideas were more fully elaborated in the following 

 year. He added the further examples : Our dray-horses 

 have arisen through the use to which they have been put, 

 and the race-horse also, which has been used in a different 

 way. Cultivated plants, on the contrary, are the result of the 

 new environment to which they have been subjected. 



In the "Philosophie Zoologique," published in 1809, Lamarck 

 has much more fully developed his theory. Here he combats 

 strenuously the idea that species are fixed. His point of view 

 may be judged by the following propositions, which he be- 

 lieves can be established : — 



1. That all organized bodies of our globe are veritable 

 productions of nature, which she has successively produced 

 in the course of a long time. 



2. That in her progress nature began, and begins still 

 every day, to produce the simplest organisms, and that she 

 still produces directly the same primitive kinds of organiza- 

 tions. This process has been called spontaneous generation. 



3. That the first beginning of animals and of plants takes 

 place in favorable localities and under favorable circum- 

 stances. An organic movement having once established 

 their production, they have of necessity gradually developed 

 their organs, and have become diversified in the course of 

 time. 



4. That the power of growth of each part of the body 

 being inherited as a consequence of the first effect of life, 



