Ewart— Variation: Germinal and Environmental. 367 
irrespective of the general condition, may be better nourished in one individual 
than another. 
Again, the ova discharged at the outset of the reproductive period may, in 
various respects, differ from ova formed later, and these may again differ from 
ova produced as senescence supervenes. 
Coming now to the second stage, the extremely important and much-discussed 
question arises—‘‘ Does the protoplasm discharged from the nucleus in the second 
polar body differ from the protoplasm retained, 7.c. is the reduction qualitative as 
well as quantitative?” If during reduction it is possible for the germ-plasm 
representing the immediate or intermediate ancestors of any individual or group 
of individuals to escape, we may have in the ‘reducing division” a sufficient 
means of accounting for a certain amount of variation.* 
During the third stage, 7c. during the time that intervenes between the 
‘reducing division” and the union with the spermatozoon, the changes which 
take place may have no small influence in settling the fate of the new individual. 
That important changes occur in ova not only before and during maturation, but 
especially after the escape of the polar bodies, may be assumed by the difference 
in the staining-reaction of the nucleus. In the newt, ¢.g., according to Watasé,f 
germ-nuclei not only stain differently throughout the whole period of their 
maturation, but also up to the end of fertilization. It almost appears as if conju- 
gation were impossible in some cases until certain chemical or physical changes 
occur in the matured ovum, or in its immediate environment. ‘The Hertwigs + 
e.g. showed that when the vitality of ova was diminished by shaking them in 
water and allowing them to stand for some time, cross-fertilization was more easily 
accomplished, while Born§ found that cross-fertilization was expedited by adding 
a superbundance of sperm. It has also been proved by Vernon that the stale germ- 
cells of echinoderms behave after a time very differently from fresh germ-cells. 
Up to a certain time the development is normal, then there is about 1 per cent. of 
abnormal blastule per hour, after which the number of abnormal blastulee may be 
nearly 20 per cent. per hour. What is, perhaps, more remarkable is, that stale 
sperms give, with fresh ova, larvee distinctly larger than when both sperms and 
ova are fresh, while stale ova with fresh sperms produce abnormally small larvee. 
* Weismann’s theory of heredity takes for granted that the germ-plasm discharged in the polar bodies 
may be quite different from the germ-plasm which remains to conjugate with the entering spermatozoon. 
It may never be possible by direct observation to prove whether this assumption is or is not warranted; 
but it may be possible by experiment to prove, on the one hand, that it isan inadequate explanation, and, 
on the other, that cumulative differences in the nutrition, ripeness, &c., of the germ-cells are sufficient to 
account for much of the variation we find in organic nature. 
+ Wilson, ‘‘ The Cell,” p. 127. { Jenaische Zeitschrift f. Medicin, vol. 19 (1886). 
§ Pfliiger’s Archiv, vol. 32, p. 403. 
