320 LAMARCK, HIS LIFE AND WORK 



always pair, they would reproduce the same features, 

 and the successive generations being confined to such 

 unions, a special and distinct race would then be 

 formed. But perpetual unions between individuals 

 which do not have the same peculiarities of form 

 would cause all the characteristics acquired by special 

 circumstances to disappear. 



" From this we can feel sure that if distances of 

 habitation did not separate men the intermixture by 

 generation would cause the general characteristics 

 which distinguish the different nations to disappear. 



" If I should choose to pass in review all the classes, 

 all the orders, all the genera, and all the species of 

 animals which exist, I should show that the structure 

 of individuals and their parts, their organs, their 

 faculties, etc., etc., are in all cases the sole result of 

 the circumstances in which each species is found to 

 be subjected by nature and by the habits which the 

 individuals which compose it have been obliged to 

 contract, and which are only the product of a power 

 primitively existing, which has forced the animals into 

 their well-known habits. 



" We know that the animal called the ai, or the 

 sloth {Bradypus tridactylus), is throughout life in a 

 condition so very feeble that it is very slow and lim- 

 ited in its movements, and that it walks on the ground 

 with much difficulty. Its movements are so slow 

 that it is thought that it cannot walk more than fifty 

 steps in a day. It is also known that the structure 

 of this animal is in direct relation with its feeble state 

 or its inaptitude for walking ; and that should it de- 

 sire to make any other movements than those which 

 it is seen to make, it could not do it. 



" Therefore, supposing that this animal had received 

 from nature its well-known organization, it is said that 

 this organization has forced it to adopt the habits and 

 the miserable condition it is in. 



" I am far from thinking so ; because I am con- 



