2 PRIMARY FACTORS OF ORGANIC EVOLUTION. 



termingled, as for instance in muscular action, where 

 both destruction of proteids and growth of muscular 

 tissue result from the same acts, or use. Physiology, 

 or the science of functions, concerns itself chiefly with 

 destruction, and hence physiologists are especially 

 prone to be insensible to the phenomena and laws of 

 progressive evolution. The building of the embryo, 

 remains a sealed book to the physiologist unless he 

 take into account the allied biological science of evo- 

 lution, as resting on the facts of botany, zoology, and 

 paleontology. In his reflections on the relations of 

 mind to matter he is likely to see only the destructive 

 functioning of tissue, and not the history of the build- 

 ing of the same during the ages of geological time. 



J. B. P. A. Lamarck 1 thus contrasts the theories 

 of direct creation, and creation by evolution. The 

 former asserts : "That nature or its author in creating 

 animals has foreseen all possible kinds of circumstances 

 in which they may have to live, and has given to each 

 species a permanent organization as well as a prede- 

 termined form, invariable in its parts ; that it forces 

 each species to live in the place and the climate where 

 one finds them, and to preserve there the habits which 

 it has." He then states his own, or the evolutionary, 

 opinion to be: "That nature in producing succes- 

 sively all species of animals, commencing with the 

 most imperfect or simple, and terminating its work 

 with the most perfect, has gradually complicated their 

 organization ; and these animals spreading themselves 

 gradually into all habitable regions of the globe,- 

 each species has been subjected to the influence of the 

 circumstances in which it is ; and these have produced 

 the habits which we observe, and the modifications of 



\Philosophie Zoologique, Paris, 1809, Vol. I., Chap. VII. 



