APPENDIX E 249 



evolution, but of reversion. As I have already indicated, it is on 

 such cases as the latter that Reversed Selection works. Thus, 

 when during the phylogeny any character becomes useless, and 

 selection ceases, retrogression ehminates it with a speed which is 

 proportionate to the speed of evolution. But, if it becomes 

 worse than useless, then an additional factor steps in to hasten 

 elimination. Reversed Selection then takes advantage of such 

 apparently atavistic, but really evolutionary, variations as cause an 

 individual, after he has represented his parent, to revert back 

 again to a remoter ancestor. Moreover, Reversed Selection not 

 only preserves such individuals, but also eliminates all such indivi- 

 duals as have the worse than useless characters in a greater degree 

 than their parent, and thus prevents them from influencing posterity. 

 It would be well to illustrate the foregoing with a concrete 

 case. Suppose we plant seeds of those garden plants which I 

 have instanced as having undergone very swift evolution. In a 

 great number of cases the young plants revert towards the 

 ancestral wild type. Now, I have enquired elsewhere, and I have 

 never heard that the seeds of such a reverted plant, or of any of 

 its descendants, have ever reproduced the cultivated type. This 

 means that the cultivated type has disappeared absolutely from the 

 series. It will never again be represented in the ontogeny, and 

 could reappear only as a consequence of fresh evolution, resulting 

 from selection as stringent as that by which the cultivated type 

 was originally evolved ; if it did reappear without fresh evolution, 

 it would be because the reversion to the wild type had resulted, 

 not from true atavism, not from a lapsing of the last steps of the 

 ontogeny, but from the false atavism on which Reversed Selection 

 works. But, since the retracement on which Reversed Selection 

 works is apparently always small in amount, it never seems to 

 occur in species that have been so rapidly evolved as these garden 

 plants. Their reversion, therefore, seems to be invariably due to 

 true atavism, there being apparently no room for Reversed 

 Selection. Here, then, is a strong proof, convincing proof, as it 

 seems to me, that true atavism means a lapsing for good and all 

 of the last steps made in the phylogeny. 



