228 The Significance of Sex. [March 
spermatozoa. By letting the eggs lie a long time in impure water 
Hertwig has so weakened this resistance as to effect hybridization 
between forms not ordinarily capable of being thus hybridized. 
But as he got results closely similar with unfertilized eggs and 
also with eggs where polyspermy of its own species took place, 
and furthermore, that polyspermy ensued in these cases of enforced 
hybridization, we must be cautious in our inferences. To leave 
eggs a long time unfertilized, instead of developing the tendency 
to fuse with any partner, ought rather to develop the opposite 
or parthenogenetic tendency. Strasburger thinks superfecunda- 
tion arises when the gametes are not sexually mature. But here 
again we have no thorough knowledge of the facts. Spermatozoa 
have also been seen to penetrate the polar globules, which is not 
remarkable, as we know that these are (when the first globule has 
divided again) the counterparts of the female pronucleus; but 
Hertwig found that the spermatozoa penetrate any globule of 
extruded yelk (whether it has a nucleus or not) when artificially 
pressed out through a riftin the egg membrane. Probably, then, 
the attraction of the spermatozoa is for the nutriment, or for the 
cytoplasm, and the nuclear attraction arises later in accordance 
with other laws. 
We see from this survey that sex in its primary sense, as in- 
hering in the nucleus, or perhaps in Strasburger’s sense as due to 
a peculiar stimulus of the cytoplasm upon the unsexed nucleus, 
sex is not an absolute condition but admits of degrees, is, in fact, 
a want, a hunger, which the cells may experience in different 
degrees. How the mixture of different characters confers vigor 
to cell-division we cannot explain. Perhaps we would be more 
general if we said that fertilization consists in broadening cell-_ 
education. Hence parasites that are cells of one idea do not need 
it to any extent. At present we cannot see how it is possible to 
explain it on physical principles. It is, however, only a confes- 
sion of ignorance to refer the problem of heredity to the domain 
of psychology; we have explained nothing in so doing. 
tozoa—Here the phenomena of fertilization are very 
ated: In the lower flagellates more than two cells may fuse; 
and polyzygosis has been observed also in Actinophrys and 
Arcella. We meh with Lankester, also place in this catagoiy 
3: ‘ ; ce 
Sg T 
