278 



Retrograde Varieties 



built up of one active and one dormant unit. 



Thirdly this deviating pair will exhibit the 

 active unit which it contains, and the hybrid 

 will show the aspect of the parent in which 

 the character was active and not that of the 

 parent in which it was dormant. Now the ac- 

 tive quality was that of the species, and its 

 latent state was found in the variety. Hence 

 the inference that hybrids between a species 

 and its retrograde variety will bear the aspect 

 of the species. This attribute may be fully 

 developed, and then the hybrid will not be dis- 

 tinguishable from the pure species in its outer 

 appearance. Or the character may be incom- 

 pletely evolved, owing to the failure of coopera- 

 tion of the dormant unit. In this case the hy- 

 brid will be in some sense intermediate between 

 its parents, but these instances are more rare 

 than the alternate ones, though presumably 

 they may play an important part in the varia- 

 bility of many hybrid garden-flowers. 



All of these three rules are supported by a 

 large amount of evidence. The complete fertil- 

 ity of varietal hybrids is so universally acknowl- 

 edged that it is not worth while to give special 

 instances. With many prominent systematists 

 it has become a test between species and vari- 

 eties, and from our present point of view this as- 

 sumption is correct. Only the test is of little 

 use in practice, as fertility may be diminished 



