428 STERILITY OF HYBRIDS. 



will (so far as this hybrid is concerned) forever end. 

 There is a definite and absolute failure of issue, with the 

 hybrid; unlike the failure of issue, in the case of an in- 

 dividual of a pure species, whose sterility is caused 

 solely by its reproductive element being modified by 

 the forces of an inadequate number of the characters of 

 its species. As Darwin has noted, from observations 

 made, the sterility of this individual is not absolute: As 

 Darwin, however, has failed to note, the reason its ste- 

 rility may be remedied, is because it needs only to mate 

 with another individual of the same species, which has 

 the complement of characters required for the purposes 

 of reproduction, or which (failing to possess such com- 

 plement) can contribute other characters which the 

 former lacks, the addition whereof to the number it 

 already possesses, may make up the number which is 

 necessary to restore fertility. 



