the Nttcleolus in Heredity. 271 
in the latter decreases, that in the former increases, and vice 
versa. For a discussion of the matter, which to be at all 
complete would have to be very lengthy, I will refer to 
Hertwig’s 1 and Wilson’s 2 standard books on the cell. Here 
it may be stated that we have the authority of Wendt, Flem- 
ming, and Hermann for this view; while A. Zimmermann, in 
his ‘ Morphologie und Physiologie des pflanzlichen Zellkernes,’ 
also quotes additional references in its favour which seem to 
render this view very probable if not certain. 
If we assume this distribution of nucleolar matter among 
the chromosomes and the integral division of the hereditary 
substance in the latter during the karyokineses taking place 
in the ontogeny (in contradistinction to the differential division 
assumed by Weismann), then the first condition as to the 
male and female hereditary masses is assured. 
But if we look to the chromatin alone and leave the nucleoli 
out of count as bearers of hereditary substance, the equivalence 
of the two masses is not so apparent, but often seems to be 
contradicted by observation. Thus it is frequently observed 
that the male nucleus immediately before fertilization is 
a compact mass of chromatin, while the female nucleus has 
but little chromatin, and is possessed of a large nucleolus. In 
many cases this difference equalizes itself after the male 
nucleus enters the ovum. Its chromatin is then apparently 
reduced and nucleoli appear 3 . But in other cases the 
difference persists up to the moment of fusion. Thus, 
according to Farmer’s 4 and Strasburger’s 5 figures, the amount 
of chromatin in the sperm-nucleus of Fucus appears to be 
much greater than that in the nucleus of the ovum. But the 
large nucleolus of the latter equalizes the amount of hereditary 
substance in the two nuclei if we admit the hereditary function 
of the nucleolus. The same may be stated regarding the 
1 Hertwig, 1. c., p. 206. 
2 Wilson, 1. c., p. 92. 
3 Cp. Guignard, Nouvelles Etudes s. 1. Fecondation, Figs. 76, 81. 
4 Cp. Farmer and Williams, Phil. Trans. Roy. Soc., 1898, B, Figs. 
20, 21. 
5 Cp. Strasburger, Jahrb. f. wiss. Bot, xxx, Taf. xviii, pp. 267, 246, 286. 
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