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Notices of Books. 
agreement with Hansen 1 , that this is due to the saponification of the 
oily solution of chlorophyll, which constitutes the oily green drops, 
the ‘ vacuoles ’ or ‘ grana,’ described above as occurring in the fibrillae. 
With regard to the action of strong hydrochloric acid, it is interesting 
to compare the author’s conclusions with those of Pringsheim. The 
colouring matter is gradually exuded as masses of chlorophyllan 
(Pringsheim’s hypochlorin), and the body of the plastid presents 
darker and lighter areas which Pringsheim interpreted as due to a 
trabecular or spongy structure. Schwarz, however, shows that 
the darker areas are granular or fibrillar masses formed by pre- 
cipitation of some of the proteid by the strong acid; hence the 
structure of the chloroplastid is not spongy or trabecular. 
Passing now to the nucleus, the author distinguishes in it the 
following components : a peripheral membrane, a ground-substance 
( Kernsaft of R. Hertwig), nucleoli, and a fibrillar framework. These, 
he finds, consist of different substances, as indicated by their reactions, 
which he distinguishes by various names. The substance composing 
the nuclear membrane is termed amphipy renin) that of the nucleoli 
pyrenin ; those of the framework and of the ground-substance, 
respectively linin and paralinin. Besides these substances there 
is chromatin , which usually occurs in the form of granules in the 
fibrillar framework of the resting nucleus. In the young nucleus, 
the chromatin is uniformly distributed throughout the fibrillar frame- 
work, though in some cases granules of chromatin are also present. 
This account of the chemical composition of the nucleus differs widely 
from that given by Zacharias 2 , according to which the nucleus 
consists of nuclein, plastin, and albumin, the first being present 
especially in the chromatin-granules, the second in the framework 
and the ground-substance, the third in the nucleoli. 
With regard to the structure and composition of the nucleus at 
different stages, the author points out that the framework consists 
at first of a single filament which, by the formation of anastomoses, 
forms a reticulum. This change is accompanied by an increase 
in size of the nucleus as a whole, due to an increase in the bulk of 
the framework and of the ground-substance, and, at first, to a growth 
of the nucleoli. But the nucleoli begin to diminish before the 
nucleus has completed its growth, so it appears <as if the substance 
1 Arb. d. Bot. Inst, in Wurzburg, III. 1884. 2 Bot. Zeitg., 1882. 
