SELECTION 189

or between fellow-kin and foreign foes—and of

the struggle between organisms and the inanimate
environment. He also emphasised the sexual selection
which occurs (a) when rival males fight or otherwise
compete for the possession of a desired mate or
mates, and in so doing reduce the leet, and (£) when
the females appear to choose their mates from amid
a crowd of suitors. While many now doubt if the
range and effectiveness of preferential mating is so
great as Darwin believed, there seems no reason to
doubt that this mode of selection has been a factor
in evolution. There are facts which warrant us
in saying that das ewzg *weibliche plays a part in the
upward march of life, that Cupid's darts as well as
Death's arrows have evolutionary significance.

Even more important, however, are other exten-
sions of the selection-idea. There may be struggle
between groups as well as between individuals, as
when one ant-colony goes to war with another, and
there may be struggle of the parts within the
organism just as there is struggle between organisms.
There is struggle when one ovum survives in an
ovary by devouring all its sister-cells, as in the case
of Hydra and Tubu/aria, and, after allowing a wide
margin for chance, there may be some form of selec-
tion among the crowd of spermatozoa encompassing
the egg which only one will fertilise, just as there
is some form of selection among the many drones
which pursue the queen-bee in her nuptial flight.
"Weismann has carried the selection-idea to a logical
finesse in his theory that there may be a struggle
between the different sets of hereditary qualities in
the germ-cell, or that there is a process of " germinalls—either between fellows of the same kinfunction included, must be in some