238 Retrograde Varieties 



as to the true value of some form, by its rela- 

 tionship to the allied types in the way of retro- 

 gressive modification. Color-differences are so 

 showy, that they easily overshadow other char- 

 acters. The white and the blue thorn-apple, 

 the white and the red campion {Lychnis ves- 

 pertina and diurna) and many other illustrative 

 cases could be given, in which two forms are 

 specifically separated by some authors, but 

 combined by others on the ground of the retro- 

 grade nature of some differentiating mark. 



Hitherto we have dealt with negative charac- 

 ters and tried to prove that the conception of 

 latency of the opposite positive characteristics 

 is a more natural explanation of the phenome- 

 non than the idea of a complete loss. We have 

 now to consider the positive varieties, and to 

 show that it is quite improbable that here the 

 species have struck out for themselves a wholly 

 new character. In some instances such may 

 have been the case, but then I should prefer to 

 treat these rather as elementary species. But 

 in the main we will have to assume the latency 

 of the character in the species and its reassump- 

 tion by the variety when originating, as the most 

 probable explanation. 



j Great stress is laid upon this conception by 

 \he fact, that positive varieties are so exces- 

 sively rare when compared with the common oc- 



