890 The American Naturalist. [October, 
that the germinal cell may not be rigidly controlled in its de- 
velopment by hereditary influences, but may have a degree of 
independence and susceptibility to the action of minor and 
local influences. As variation cannot well be due to influen- 
ces proceeding from the parental organisms, it certainly seems 
as if it must arise from conditions existing in the environment 
of the developing germ and embryo, or to internal molecular 
forces, left free to produce variations by a degree of weakness 
in the hereditary influences. 
Much certainly depends on the inherent conditions of the 
reproductive cells. These may vary in developmental energy, 
through excess or deficiency of nutrition. They may also vary, 
through position or otherwise, in the quantity of nutriment ob- 
tained during development. In consequence, there is probably 
an active struggle for existence at this low level of life, the num- 
bers involved being considerable, while—in the case of the high- 
er animals—only one ora few can survive. This early competi- 
tion would seem simply to be one of comparative cell vigor, or 
of advantage in propinquity to the store of nutriment; but it 
is, perhaps, not quite so simple. The germinal cell is, to out- 
ward appearances, a largely homogeneous organism, but the 
facts of development prove that it is heterogeneous in constitu- 
tion, its tendencies and powers being not single but multiple. 
It probably is made up of various groups of molecules differ- 
ently arranged or organized, each of which is destined, in its 
development, to produce a special organ or variety of tissue in 
the mature form. What we can see very poorly indicates 
what exists. The compound of organs‘into which the cell un- 
folds indicates that conditions preliminary to those organs 
existed in it, each perhaps located in some definite region of 
the cell, which may thus be made up of distinct groups of 
differently organized molecules. 
If this, as we have much reason to believe, is the case, the 
field of competition may be a much more extended one than 
has been supposed. In addition to competition for nutriment 
between cells as wholes, there may be an internal competition 
in each, between its different molecular groups, while differ- 
ences in original strength may give some of these an advan- 
