172 Gardner— Studies on Growth and Cell 
According to this, Hertwig’s first condition is assured, for 
if chromatin alone were regarded as the bearer of hereditary 
substances the equivalence cannot be retained. 
The second condition is likewise assured. The hereditary 
mass being composed of nucleoli and chromatin, is equally 
distributed, during karyokinesis, among the cells derived from 
the fertilized ovum. 
Those who consider the chromatin to be the sole hereditary 
substance believe that the elimination of hereditary substance, 
which would be necessary to prevent a summation of the 
hereditary masses, is effected by the so-called “division with 
reduction.” But this latter theory is not yet established on 
a sure basis. 
The fourth condition affects Strasburger’s nuclear hypothe- 
sis and the proposed extension of it equally. 
Therefore, judged from Hertwig’s criterion, this theory 
regarding the chromatin and nucleolus, as hereditary in func- 
tion, finds no objections. 
Mature tissues contain relatively a large amount of nucleolar 
substance and a relatively small amount of chromatin. As 
the cell becomes specialized, the chromatin is reduced in 
quantity until the idioblasts representing the special properties 
of the mature cell are alone present. 
The great surface of the chromatin as compared with the 
small surface of the nucleolar substance favors the view that 
chromatin may be composed of active idioblasts. The greatly 
attenuated thread, described by Rosen, is explained readily by 
this theory. This long chromatin thread is immersed ina 
nuclear fluid containing a large amount of nucleolar substance 
suspended in it, and thus a uniform distribution of idioblasts 
along this thread is possible. The persisting portion of the 
nucleolus contains that portion of hereditary substance which 
is to be got rid of and not to appear in succeeding generations. 
The transformation of the nucleoli, bodily into nuclei, in 
