1898] A THHORY OF RETROGRESSION 401 
that A B C D represent a line of individuals; then if D reverts to 
B, that is if D varies from his parent C in such a way that in his 
ontogeny he represents the life-history of the race only up to the 
point reached by B, omitting the additional characteristic of C, 
it is evident from the point of view of heredity, that the series 
becomes A B D; or rather it becomes A B, since in effect, D is B. 
C then disappears completely and for ever from the series; and it 
follows that, if the characters of C ever reappear in E, or any sub- 
sequent member of the series, they must do so as a result of fresh 
evolution, not as a result of reversion. It is necessary to emphasize 
this point for on it my whole argument depends. If D, on the 
other hand, varies in such a manner from C that after representing 
C, that is after recapitulating the whole of the phylogeny he reverts 
back to B, then C does not disappear from the series. C will still 
be represented in the ontogeny, and, if his characteristics reappear 
in any individual at the end of the ontogeny, that is in the adult, 
it will be as a result, not of 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 eliminates 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 the 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 individuals as have the worse than useless 
characters in a greater degree than their parent, and thus pre- 
vents 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 everywhere, 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, 
