370 Appendi.v 



and physical conditions that obtained in the primordial 

 environment when life first appeared on earth. 9 



But it is easily seen that our theory is limited to a 

 consideration of the tendency to invariability only so far 

 as it manifests itself each moment in the behavior of 

 each individual. Therefore instead of serving as a 

 far too one-sided starting point for the explanation of 

 the evolution of species it forms the basis upon which 

 all the most important affective tendencies of the animal 

 world may be built up. 



As a factor of invariability for the individual, this 

 tendency to preserve its stationary physiological condi- 

 tion is indeed one of the most important factors in the 

 variation and progress of the species, but in quite a 

 different way from that pointed out by Quinton. For 

 from this tendency arose and developed the power of 

 motion which is the greatest difference between plants 

 and animals, and with which also has kept pace the 

 development and perfection of the whole motor ap- 

 paratus, including that of the nerves and senses, which 

 plays so important a part in determining the character- 

 istics which distinguish the different zoological species. 

 Finally as a factor of individual invariability it has 

 proved by its effect on man to be one of the most con- 

 spicuous factors in all social evolution, for we may 

 well say that technical inventions and industrial products 

 from the first cave dwellings, the first skins used for 

 clothing, the first discovery of fire to the most complex 

 attainments of to-day have tended constantly more or 

 less directly or indirectly towards one single goal, 



9 R. Quinton, L'eau de wier, milieu organique. Especially Book 

 II, "Loi generate de Constance originelle," pp. 429-456. Paris, Mas- 

 son, 1904. 



