GENERAL CONCLUSIONS 321 



the most recent, and that consequently degeneration 

 always retraces the path of progress. Evolution 

 is irreversible, and accordingly, with a few more 

 or less obvious exceptions, we draw the following 

 conclusions : 



1. That an institution or an organ which has 



once disappeared never reappears. 



2. That an institution or organ once reduced 



to the condition of a vestige cannot be 

 re-established and resume its former func- 

 tions. 



3. Neither can they assume fresh functions. 



III 



Degenerative evolution is brought about by a 

 limitation in means of subsistence either in 

 nutriment, capital or labour. In biology the prin- 

 cipal if not the sole agents in its accomplishment 

 are the struggle for existence between the various 

 organs, and the struggle for existence between the 

 various organisms. 



In sociology it is artificial selection which is the 

 dominating agent, and natural selection plays only a 

 secondary part. 



The occasional causes of degenerative evolution 

 are inutility of function, insufficiency of nutri- 

 ment or resource, and (in biology only) lack of 

 space. 



x 





