238 
REV. J. T. GULTCK OX DIVERGENT EVOLUTION 
almost certainly been propagated iu a state of nature for thousands 
of generations without having been once intercrossed.” * 
General Observations on Germinal ancl Floral Segregation. 
A fact of great importance in its bearing on the origin of 
varieties should be here noted. Any variation, arising as a so- 
called sport, in any group of plants where either of these prin- 
caples is acting strongly will be restrained from crossing, and will 
be preserved except in so far as reversion takes place. Now 
there is always a possibility that some of the segregating branches 
of descent will not revert, and that, through the special character 
which they possess in common, they will some time secure the 
services of some insect that will give them the benefit of cross- 
fertilization with each other without crossing with other varieties. 
The power of attaining new adaptations may be favoured by self- 
fertilization occasionally interrupted by interbreeding with indi- 
viduals of another stock ; for the latter is favourable as intro- 
ducing vigour and variation, and the former as giving opportunity 
for the accumulation of variations. 
(Jb) Impregnational Segregation. 
Impregnational Segregation is due to the different relations in 
which the members of a species stand to each other in regard to 
the possibility of their producing fertile olfspring when they 
consort together. 
In order that Impregnational Segregation should be established 
and perpetuated it is necessary, 1st, that variation should arise 
from which it results that those of one kind are capable of pro- 
ducing vigorous and fertile offspring in greater numbers when 
breeding with each other than when breeding with other kinds ; 
2nd, that mutually compatible forms should be so brought to- 
gether as to ensure propagation through a series of generations. 
In order to secure this second condition, it is necessary that, in 
the case of plants, there should be some degree of Local, Germinal, 
or Floral Segregation, and, in the case of animals that pair, 
either pronounced Local Segregation, or partial Local Segre- 
gation supplemented by Social or Sexual Segregation. The first 
of these factors I call Negative Segregation, as contrasted with all 
* See ‘Cross- and Self Fertilization in the Vegetable Kingdom,’ p. 439. 
