CHAPTER... 
THE DEVELOPMENT OF THE INDIVIDUAL 
HUMAN BEING 
ALTHOUGH in adult life a man is about thirty times as 
heavy as a fowl, the human egg weighs less than a mil- 
lionth as much as that of the hen, and is less than a 
hundredth of an inch in diameter. This great disparity 
is appropriate to the great difference in the method of 
nourishing the unborn progeny. The essential nucleus of 
the living germ-cell in either case makes up but a trifling 
portion of the total weight of the egg. A great portion of 
the egg substance in the fowl consists of the. yolk which 
gives nourishment to the forming creature. This egg 
nourishment must entirely suffice to sustain growth 
throughout the three-weeks’ period of gestation preceding 
the birth of the chick. The human embryo, on the con- 
trary, almost immediately attaches itself to the wall of 
the uterus and begins to be nourished at the expense of its 
mother’s circulation. 
The nucleus of the human germ-cell within the egg is 
microscopic in its size and, though it is considerably 
larger than the male nucleus which unites with it to in- 
itiate the new individual, the two contain essentially the 
same number of chromosomes which constitute the in- 
heritance material. With this in mind, and reflecting 
that the subsequent office of the mother is mainly to 
nourish the growing embryo, it will not appear so strange 
that on the average the influences of father and mother on 
the character of their offspring are substantially equal. 
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