206 APPENDIX II—INTENSIVE SEGREGATION. 
on adaptation for overcoming, outdoing, or supplanting others of the 
same species, should be clearly distinguished and named. We further 
note that there can be no doubt that dominational selection acting 
for many generations on sections of a species that are prevented from 
intercrossing will in all probability follow somewhat different lines. 
In other words, zndependent dominational selection will produce diver- 
gent evolution. 
(14) *Impregnational selection—The codrdination between the pollen of a 
given species and the stigma and ovules of the same species must be kept up by a 
process of selection, resulting from the failure to propagate of the individuals whose 
pollen is least potent, and of those whose ovules are most difficult to fertilize. 
This we may appropriately call potential selection; and it will be convenient to 
class it with forms of selection securing other coérdinations necessary for success- 
ful impregnation. These other forms are: dimensional selection, of which we 
have an example in the codrdination between the length of the pollen tubes and 
of the pistils; also fecundal selection, illustrated by the different degrees of 
survival secured by variation in the number of the ovules and in the quantity and 
methods of distribution of the pollen grains; and, as illustrated, in many species 
of insects, structural selection, due to the success gained through superior co6rdi- 
nation of the organs by which males and females clasp each other. Impregnational 
selection is an important form of reflexive selection. I wish here to call especial 
attention to the importance of fecundal selection. 
(15) Fecundal selection produces intensive segregation with diver- 
gence through independent fecundal intension, in isolated sections of 
aspecies. Itis the form of selection that results from propagation 
according to degrees of fertility. Asit involves not only the superior 
propagation of the more fertile, but the inferior propagation of the 
less fertile and the non-propagation of the least fertile, it may be 
described as the exclusive propagation of the more fertile through 
the failure to propagate of the less fertile. It would avail nothing in 
determining the form that is to prevail in succeeding generations if it 
did not in some degree preclude the crossing of the less fertile with the 
more fertile; but, as it is evident that, so long as increased fertility is 
not a disadvantage, the more fertile half of the species will leave a larger 
number of offspring than the less fertile half, it follows that when the off- 
spring have come to maturity a larger portion of the fertile will consort 
with the fertile than in the previous generation; and so the fertility of 
the following generation will be still further increased. The chief check 
to this law of cumulative fertility is found in the correlative law of 
cumulative adaptation through adaptational selection. The combined 
action of these two laws results in the troumphant development of the most 
fertile of the best fitted or the best fitted of the most fertile. 

*As this paragraph does not occur in the original paper it is printed in 
different form. 
