1885.1 
Fecundation of Animals. 
23 
in their structure, the pronuclei differ in nothing from ordi- 
nary nuclei, it is clear that, physiologically speaking, they 
are in no wise equivalent to nuclei. Each pronucleus is 
rather equivalent to a half-nucleus which presents, from its 
origin, a uni-sexual character. This is the justification for 
the term “ pronucleus,” which I originated, and which is 
now generally adopted. But if the female pronucleus is 
not the equivalent of an ordinary nucleus it is clear that 
the yolk-globe, with its pronucleus, is not a cell. If a par- 
ticular name for the nuclear element is justifiable, it is, in 
like manner, for the cell-body. I propose, therefore, the 
name “ female gonocyt ” for the yolk-globe with its pro- 
nucleus. 
As for the spermatozooid it is distinguished by many 
peculiarities from every true cell-element. We never ob- 
serve the division of a spermatozoon. Its nuclear element 
becomes a pronucleus, and is therefore not equivalent to a 
nucleus. Hence the body of the spermatozooid is not a 
cell, and it may be suitably known as a male gonocyt. This 
element is distinguished in its origin from every other cell 
by the circumstance that the spcrmacyt, from which it is 
derived, becomes a spermatozoid only by divesting itself of 
a part of its substance. The part thus thrown off by the 
spermatocyt is the cytophor, or more corredtly the cytophoral 
portion. 
I do not need to revert here to the view which I have ad- 
vanced above concerning the signification of the phenomenon 
of fecundation. I am of opinion that that fecundation con- 
sists essentially in the completion cf the female gonocyt and 
its transformation to a cell, — that is, in the replacement of 
the eliminated elements of new matter derived from the 
spermatozoon. The eliminated nuclear elements (polar 
vesicles) are replaced by the male pronucleus ; and as the 
polar vesicles together with the female pronucleus formed a 
cell-nucleus, the germinal vesicle in like manner, the male 
pronucleus, and the female pronucleus form together a single 
cell-nucleus. It is indifferent whether these two pronuclei 
coalesce visibly to a single element, or if they remain dis- 
tinct. There exist grounds for the assumption that even in 
the ordinary nuclei the male chromatine remains separate 
from the female chromatine. 
The protoplasm of the male gonocyt is mingled likewise 
with the body of the female gonocyt. But is this a substi- 
tution ? Is it in the same sense essential as the substitution 
of a part of the nucleus ? The question may be discussed, 
but for the present it is hard to decide. 
