346 ZOOLOGICAL PHILOSOPHY 



absorbed substances make good the losses which they suffer as a 

 consequence of life, and serve in addition for the individual's growth. 



I have said that the subtle fluids which move in the interior of these 

 living bodies cut out special routes which they continually follow, and 

 thus begin to estabhsh definite movements which become habits. Now 

 if we reflect that organisation develops as Ufe goes on, we shall under- 

 stand how new routes must have been cut out, increased in number, 

 and progressively varied for the furtherance of the movements of 

 contraction ; and how the habits to which these movements give 

 rise then become fixed and irresistible to a corresponding extent. 



Such, in my opinion, is the cause of movements in the most imperfect 

 animals ; movements that we are led to attribute to their own initiative, 

 and to regard as a result of their faculties, because we know that in 

 other animals the source of them is within their bodies ; movements, 

 in short, which are carried out without any will on the part of the 

 individual, and which yet, from being very irregular in the most 

 imperfect of these living bodies, gradually become more regular and 

 are always the same in animals of the same species. 



Finally, just as reproduction transmits acquired forms both internal 

 and external, so too it transmits at the same time an aptitude for 

 certain specialised types of movement and corresponding habits. 



Of the Transference of the Force, which produces Move- 

 ments, INTO THE Interior of Animals. 



If nature had confined herself to her original method, that is, to a 

 force entirely external and foreign to the animal, her work would 

 have remained very imperfect ; animals would have been simply 

 passive machines, and nature never would have produced in such 

 organisms the wonderful phenomena of sensibility, the intimate 

 feehng of existence, the power of acting and, lastly, ideas, by means of 

 which she has created the most astonishing of all, viz. thought or 

 intelKgence. 



With the intention of reaching these great results, she gradually 

 prepared the way by increasing the coherence of the internal parts of 

 animals, by diversifpng their organs, and by multiplying and com- 

 pounding their contained fluids, etc. ; thereafter she was able to 

 transfer into the interior of these animals that force productive of 

 movements and actions, which in truth they did not originally control, 

 but which was in great part rendered available for them as their 

 organisation became more perfect. 



Indeed, when the complexity of animal organisation had gone so 

 far as to establish a nervous system of a certain development, as among 

 the insects, then animals provided with this organisation were endowed 



