190 Notices of Books . 
of the nucleoli were used in the formation of the other portions of 
the nucleus. The chromatin is very abundant at first, but it does 
not seem to increase in proportion to the growth of the nucleus. 
After it has attained its full size, the nucleus begins to diminish. 
The framework has either more delicate fibrillae, or some of them 
disappear altogether, so that the reticulum becomes much looser, 
and the granules of chromatin are few. In fact, all the con- 
stituents of the nucleus diminish in quantity, but no one of them 
disappears. 
It is convenient to defer an account of the reactions of these 
various substances for the present, but it may be mentioned here 
that in some cases the author observed complete solution of the nucleus 
on treatment with water, but only in very young cells. In older 
nuclei the effect of water was to cause swelling-up and vacuolation, 
accompanied by the solution of certain of the constituents, especially 
the paralinin. In some cases treatment with water caused no per- 
ceptible change ; this appeared to be due to the action of the tannin 
or acid dissolved in the cell-sap. 
The author does not give any satisfactory explanation of the 
difference in treatment with water between young and older nuclei. 
The inference to be drawn from his remarks is, that the same sub- 
stances are present in both, but in somewhat different forms. For 
instance, in controverting the conclusion of Zacharias that the 
nucleoli consist of albumin and plastin, the author suggests that 
they consist of two forms of pyrenin, one more soluble, the other 
less so, and that the former predominates in young, the latter in old 
nuclei. But this suggestion appears to beg the question. The 
general conclusions at which the author arrives are based mainly 
on the differences in solubility of the various substances which he 
distinguishes, and if this criterion is not admitted in this case, why 
should it be admitted in the others ? 
Coming now to the cytoplasm, the author concludes that the 
fibrillar structure which has been described by Schmitz and others 
is not normal, but is the result of precipitation or of vacuolation. 
In support of this view, he gives figures of precipitates obtained by 
the action of alcohol and other reagents on solutions of albumin, 
peptone, gelatin, etc., as well as of precipitates produced in both 
the protoplasm and the cell-sap of living cells by various chemical 
reagents as well as by electric shocks. 
