ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
443 
IV. The substance so permeated is solid and of high refractivity 
0*>l-53). 
V. In death the solid substance forms a sort of reticulum too fine 
for resolution by our Microscopes,* the interstices of which are permeated 
by the watery liquid ; in life the two are physically combined in the 
form of a viscid liquid. Hence death is essentially a phenomenon of 
precipitation. 
Tor the more exact solution of the points discussed above, I propose 
making a full research on the refractivity of various proteids, solid and 
in solution, and of living and dead structures, animal and vegetable. 
The method I shall follow is that adopted by Exner in the papers cited 
above, consisting in immersion in liquids of known refractivity, and 
examination under the Microscope with the micro-refractometer which 
he invented. 
It may be of interest to add that the above ideas were suggested to 
me in elaborating a technique for the convenient study of the Sapro- 
legnieas. 
Peculiar Polycentric Arrangement of Chromatin. f — Dr. 0. vom 
Rath calls attention to a peculiar poly centric arrangement of chromatin 
which he noticed in some large gland-like cells of Anilocra mediterranea. 
These cells were found in various parts of the head, and the author is 
inclined to believe that they have a salivary function. The cells varied 
considerably in size and form. The cell-protoplasm has in most cases 
the appearance of a finely granular coagulation, in which a very fine 
multireticulate plexus may occasionally be made out. In most cells 
there are several nuclei, and they may be of very different sizes. Some 
are round, others oval, others sausage-shaped, biscuit-shaped, or con- 
stricted. The chromatic star-figures exhibit a polycentric arrangement 
of the chromatin of the nuclei ; each of these figures consists of an 
intensely coloured centre and a number of radially arranged, somewhat 
brightly-coloured chromatin-rods. The centre generally appears to be 
homogeneous, while in very thin sections it has not rarely the form of a 
dark ring with a clear central internal space. All the chromatin-rods 
are considerably thinner at the end which is turned towards the centre 
than at the other, which is somewhat swollen. At first sight there does 
not seem to be a direct connection between the chromatin-rods and the 
centre, but the use of higher powers (Seibert’s apochromatic homog. 
immers. N.A. 1-35, oc. 8) shows distinctly that the club-shaped 
chromatin-rod is continued, at its central end, into a thin, pale filament 
which extends to the dark centre. The chromatin-rods surround the 
centre in all directions like the spines of a sea-urchin. 
In nuclei with one star the centre of the nucleus and of the star fall 
together ; but when there are several stars the centre of each is about 
the length of the radius of a star from the periphery of the nucleus. 
From the peripheral end of the several chromatin-rods, very pale, fine 
filaments pass out ; these unite the chromatin-rods of the same star with 
one another, and with those of the neighbouring stars ; in this way a 
plexus is formed which traverses the whole nucleus. 
* Of course this is quite distinct from the much coarser reticulum or sponge 
directly visible under the Microscope. 
t Zool. Anzeig., xiii. (1890) pp. 231-8 (1 fig.). 
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