672 The Theory of Sex and Sexual Genesis. 
This result is brought about by the accession to it of aspem 
cell, which represents a relative preponderance of the factor d 
cell-division, and the development is then begun with that dege 
of energy which is necessary to insure its going on to completion — 
In every species of organisms a certain mean adjustment of ther 
two factors to each other is suitable to the formation of ona i 
and tissues having the requisite structural characters, after Ge 
first stages of the development have been passed through M 
the germ-cell there is a departure from this mean standart ; 
of adjustment in one direction, and in the sperm-cell a departe® — 
in the opposite direction; the departure in the one case beag : 
necessary to the formation of a single aggregate of sufficient sit | 
to serve as the basis of the development, and the departure in te 
other case being necessary to the formation of germinal mate — 
fitted to restore the balance by its union with the larger agy> 
gate. This I believe to be the fundamental principle in the theory 
of sexual genesis. 1 
But in parthenogenesis the germ-cell undergoes developas 4 
without impregnation by a sperm-cell; and at first R may appe® > 
that the theoretical conclusion here arrived at 1s a 
with this fact. It may be shown, however, that it is not. : 
first place, parthenogenetic eggs or germ-cells are 
smaller than eggs that require fertilization. In the second re - 
whether they are smaller or not, the individuals den 4 
them do not generally if ever attain to as high a grade Pai a 
zation as those developed from impregnated ganai pat : 
spicuously is this the case in plants, that Sachs epee 
pretation of the phenomena and advantage of sex K 
this observed difference. In the third place, the normal a w 
between the two factors of the developmental pa + 
in nil 
restored in the germ cell, but not so completely ook oe? 
besides impregnation by a sperm-cell. This may from tht 
freer access of oxygen to it after it has been 1s! other ate 
producing organ ; by its absorption of water, with ey 
in solution, which have a tendency to set up active ap dts 
it; or by its being subjected to a higher tenp "desi 
which it was kept during its formation. By one ficient 
of these changes of conditions the balance gt not 50 
restored to cause the development to §° py 
pletely restored as it is by the accession to em 
l 
; 
} 
i 
