THROUGH CUMULATIVE SEGREGATION. 
237 
influence of this latter factor is found in its prolonging and 
fortifying the separate breeding of varieties that have arisen 
under Local, Social, or Industrial Segregation, and in thus con- 
tinuing the necessary condition for the development of increas- 
ingly divergent forms of Intensive Segregation, under which the 
organism passes by the laws of its own vital activity when dealing 
with a complex environment in groups that never cross. 
12. Germinal Segregation is caused by the propagation of the 
species by means of seeds or germs any one of which, when 
developed, forms a community so related that the members breed 
with each other more frequently than with the members of other 
communities. If the constitution of any species is such that the 
ovules produced from one seed are more likely to be reached and 
fertilized by pollen produced from the same seed than by pollen 
produced from any other one seed, then Grerminal Segregation is 
the result. 
In order to secure this kind of Segregation it is not necessary 
that the flowers fertilized by pollen from the same plant should 
be more fertile, or the seeds capable of producing more vigorous 
plants than the flowers fertilized by pollen from another plant. 
All that is required is that of the seeds produced a larger number 
shall be fertilized by the pollen of the same plant than by the 
pollen of any other one plant. 
This form of Segregation is closely related to Local Segre- 
gation on one side, and to Social Segregation on the other. It, 
however, differs from the former in that it does not depend on 
Migration or Transportation, and from the latter in that it does 
not depend on social instincts. 
13. Floral Segregation is Segregation arising from the closest 
form of self-fertilization, namely the fertilization of the ovules of 
a flower by pollen from the same flower. 
Many plants that in their native haunts are frequently crossed 
by the visits of insects depend entirely on self-fertilization when 
transported to other countries where no insect is found to per- 
form the same service for them. The common pea ( Pimm 
sativum) is an example of a species that habitually fertilizes 
itself in England, though Darwin found that it was very rarely 
visited by insects that were capable of carrying the pollen.* 
Darwin also mentions Ophrys apifera as an orchid which “ has 
See ‘ Cross- and Self-Fertilization in the Vegetable Kingdom,’ p. 161. 
LINN. JOURN.- — ZOOLOGY, VOL. XX. . 19 
