28 THEORY OF EVOLUTION 



eartli slowly changed — as the carbon dioxide 

 conten.ts in the air altered — as land aj^peared — 

 and as marine animals left the water to inhabit 

 it, they or tlieir embryos responded to the new 

 conditions and those that responded favorably i 

 gave rise to new creations. As the environ- 

 ment changed the fauna and flora changed — 

 change for change. Here we have a picture of ' 

 progressive evolution that carries with it an 

 idea of mechanical necessitv. If there is anv- 

 thing mystical or even improbable in St. Hi- 

 liare's argument it does not appear on the sur- 

 face ; for he did not assume that the response to 

 the new environment was always a favorable 

 one or, as we say, an adaptation. He expressly 

 stated that // the response was unfavorable the 

 individual or the race died out. He assumed 

 that sometimes the change might be favorable, 

 i.e., that certain species, entire groups, would 

 respond in a direction favorable to their exist- 

 ence in a new environment and these would 

 come to inherit the earth. In this sense he an- 

 ticipated certain phases of the natural selection 

 theory of Darwin, Init only in part; for his 

 picture is not one of strife within and without 



