CONCLUDING REMARKS. 453 



incontestably that not merely are those phenomena in- 

 consistent with his suppositions, but that the very con- 

 verse and refutation of them prevails. They show 

 that the sterility of hybrids, is "a special endowment," 

 and that, instead of the sterility of hybrids having 

 been induced by slowly acquired modifications, it is 

 the lessened fertility of individuals of the , same spe- 

 cies, which has been induced by modifications, and 

 that not only do such modifications operate in a way 

 the very reverse of that required by his gratuitous 

 supposition; but, in proportion to his Divergence of 

 Character (which he fain would believe evolves varie- 

 ties in distinct species), do those varieties become of 

 lessened fertility and of lessened vigor, culminating 

 very soon in death and extinction. 



Thus, from four several quarters of the science of 

 Biology — namely, first, from the phenomena of Re- 

 version which fix a limit to positive Variations ; 

 second, from the phenomena of Interbreeding which, 

 in the opposite direction, fix a limit to negative Varia- 

 tions, by entailing evil effects upon any organism in 

 proportion to the modification of the perfect type of 

 the given species, which such individual has suffered, 

 which evil effects amount to complete sterility and ex- 

 tinction, at a point which is comparatively a very 

 small remove from such perfect type; thirdly, from 

 the phenomena of Crossing, which show that only in 

 proportion as an individual regains the features which 

 it lacks, and recovers the lost integrity of its species 

 (whether the same be effected by direct Variation, by 

 Crossing, or by Grafting), does it regain its lost physi- 

 39 



