SUMMARY. 311 



quality. Independently of the question of fertility, 

 in all other respects there is the closest general resenil)lance 

 between hybrids and mongrels, in their variability, in tlieir 

 power of absorbing each other by repeated crosses, and in 

 their inheritance of characters from both parent-forms. 

 Finally, then, although we are as ignorant of tlie precise 

 cause of the sterility of first crosses and of hybrids as we 

 are why animals and plants removed from their natural 

 conditions become sterile, yet the facts given in this 

 chapter do not seem to me opposed to the belief tha*. 

 species aboriginally existed as varieties. 



