The Facts of Sex in Relation to Metabolism. 271 
fertilising substance, except in so far as the sperm-nucleus 
restores to the ovum a certain quantum of nuclear substance 
(equivalent to that lost in forming polar globules), thus 
rendering its quantity sufficient for development. To put 
it more concretely, he believes that two female pronuclei in 
an ovum might be quite as effective as the normal male and 
female pronuclei, and accepts Boveri’s remarkable observation 
that the nuclei of two spermatozoa introduced into a de- 
nucleated ovum of an Lchinus were sufficient to result in 
development. 
In short, Weismann holds “in opposition to the rejuven- 
escence theory, that there is no polar antithesis, and that, 
in the union which is the essence of fertilisation, the nuclear 
loops contribute neither male nor female principle, but a 
paternal and maternal substance, and that the significance 
of fertilisation is nothing more nor less than a mingling of 
the hereditary tendencies of father and mother.” 
(a) The Significance of Maturation.—According to Weis- 
mann’s original hypothesis as to meaning of polar globules, 
_the first division of the germinal vesicle was a removal of 
purely ovogenetic idioplasm, the second was a halving of the 
number of ancestral units contained in the germ-plasm 
proper. 
But O. Hertwig, in an exceedingly valuable research, has 
recently drawn attention to the remarkable parallelism 
between ovogenesis and spermatogenesis, observing that in 
both cases a similar “reduction division” of the nuclei takes 
place. Thus in Ascaris megalocephala, var. bivalens, the 
subject of so many famous investigations, the primitive 
reproductive cells of both sexes have four chromatin rods; 
in both cases these are first multiplied into eight, and then 
twice halved, so that there remain only two alike in 
spermatozoon and in female pronucleus. Moreover, Hertwig’s 
researches “prove that the nuclear idioplasm of all polar 
bodies, as well as that which is retained in the egg, must 
be germ-plasm.” 
Accepting Hertwig’s observations, Weismann acknowledges 
that his “previous interpretation of the first polar body as 
the removal of ovogenetic nucleoplasm from the egg must 
