
No. 458.] PARTHENOGENESIS. 67 
nothing, and that we keep in sight a part, only, of the whole 
phenomenon when we speak of fertilization as the union of | 
nuclei. Bresslau (:04) supports nearly the same view, and dis- 
tinguishes between ** Besamung,” or the entrance of spermatozoa 
into the egg, and * Befruchtung " or fertilization in the sense of 
Hertwig, Weismann, and others, 7. ¢., the union of the nuclei. 
In one respect Bethe and Bresslau are right, that is, as to the 
necessity of distinguishing between these two phenomena; but 
it remains to decide which of the two phenomena exerts the 
greater influence upon the development of the egg and may 
therefore be considered the one essential to fertilization. This 
question seems to me easy of solution in the light of recent 
experiments and observations, There can exist no doubt as to 
the importance of the union between sperm- and egg-nuclei. 
The normal number of chromosomes is indispensable to normal 
development. The paternal hereditary characters are trans- 
mitted to the descendant by the chromosomes of the sperm- 
nucleus. Even if the protoplasm of the spermatozoön, in those 
cases where it succeeds in entering the egg (for it is frequently 
cut off by the suddenly formed yolk-membrane), should possess 
the power of transmitting by heredity certain paternal qualities, 
yet, in the presence of the egg-centrosomes, it loses that power. 
Nor can there be doubt as to the importance of the part taken 
by the sperm-centrosome. It gives the stimulus to development 
and controls the successive divisions. Without it there can be, 
no development ; when hindered in the normal performance of 
its functions, abnormal development results. 
We now turn our attention to the phenomenon of the entrance 
of spermatozoa into the egg. Does it make any difference in 
the development of an egg whether one or several spermatozoa 
enter it? No, for the nucleus of only one spermatozoön 1s 
destined to unite with that of the egg. In those cases where 
_ polyspermy exists normally, all spermatozoa with the exception 
of one are gradually absorbed by the egg-protoplasm, and the 
resulting development is the same whether the spermatozoa are 
many or few; but when, as sometimes happens, they en not 
absorbed by the egg-protoplasm, their centrosomes form inde- 
pendent centers for cell-division, thus interfering with the nor- 
