72 ESSAY ON CLASSIFICATION. 



physical agents as the structure itself, with which it is so 

 closely connected, both bearing similar relations to these 



agents. 



Life is regulated by a quantitative element in the 

 structure of all organized beings, which is as fixed and 

 as precisely determined as every other feature depending 

 more upon the quality of the organs or their parts. This 

 shows the more distinctly the presence of a specific, im- 

 material principle in every kind of animals and plants. 

 All begin their existence in the condition of ovules of a 

 microscopic size, which exhibit a wonderful similarity of 

 structure. And yet these primitive ovules, so identical 

 at first in their physical constitution, never produce any 

 thing different from the parents ; and all reach respec- 

 tively, through a succession of unvarying changes, the 

 same final result, the reproduction of a new being iden- 

 tical with the parents. How does it happen then, that, if 

 physical agents have such a powerful influence in shaping 

 the character of organized beings, we see no trace of it in 

 the innumerable instances in which these ovules are dis- 

 charged into the elements in which they undergo their fur- 

 ther development, at a period when the germ they con- 

 tain has not yet assumed any of those more determined 

 characteristics which distinguish the full-grown animal 

 or the perfect plant 1 Do physicists know any law of 

 the material world which presents such analogy to these 

 phenomena, that it could be considered as accounting for 

 them ? 



In this connection, it should be further remembered 

 that these cycles of size characteristic of different fami- 

 lies are entirely different for animals of different types, 

 though living together under identical circumstances. 



