782 The Theory of Sex and Sexual Genesis. [ August, : 
does not become sufficiently pronounced to produce any percep- 
tible effect until a certain stage in the development of the embryo 
is reached. And the sex is no doubt subject to the controlling 
actions of external conditions for a time after the development 
begins, where the conditions of development, as they immediately 
affect the embryonic basis of the generative organs, can in this 
manner be considerably modified one way or the other. 
In some of the lower animals, as will be shown farther on, the 
sex is subject to control at a very late stage in the life-history of 
the individual; and toa less extent this seems to be the case 
also with plants. 
Causes Determining Sex—Since germ-cells are very large and 
sperm-cells are smail, it may at once be inferred that where they 
are formed in different parts of the organism, the parts in which 
germ-cells or their producing organs are formed must be parts m 
which the conditions are especially favorable to nutrition; and 
that the parts in which sperm-cells or their producing organs are 
formed, must be relatively unfavorable to nutrition and favorable 
to cell-division. Observation shows this to be the case; and 
from the causes thus indicated as determining the development of 
one or the other or of the two kinds of generative cells or organs, 
in different parts of the same organism, some of the causes mày 
be inferred which act to determine the sex of the individual, 
where the sexes are separate, and the truth of the inference tested 
by the results of observation and experiment. There is evidence, 
however, that the sex of the individual may also be determ : 
by the state of maturity at which the ovum has arrived peer? 
is impregnated ; and the true theory of sex must be capable 
explaining this fact. ; 
I will now give such evidence, of various kinds, as I have been 
able to obtain on the causes which determine the sex, for per 
pose of showing its agreement with the theory of ee pwe 
the earlier parts of this article. The hypothesis, it S$ ok 
remembered, is, that it is a relative preponderance of Ey p on 
tions on which cell-growth depends, or of the conditions 
: ation of the 
which cell-division depends, which causes the pele d 
female or male generati organs or determines tae eo 
g ive g Hak either fac 1 
the individual. If, therefore, the conditions on 7 
tor of the developmental process depends remain 
requisite preponderance, one way or the other, may 
con 
RE E SE Pe MTS a en, ME Ear eR, IF V EN NETS OMY T 
oa 
Nie 
sa 
still result : 
t 
Ee. 
