Miscellaneous. 479 
the ovum in the dace. We now propose to give an account of the 
curious phenomena which we have observed in the division of the 
cells of the blastoderm during the first days of the development of 
the embryo. 
Method.—Before proceeding to the examination of our results, we 
must say a few words as to the method which we employed in order 
to determine their precise signification. The embryos, after being 
liberated from their shells, were fixed in Flemming’s fluid, and the 
sections were treated in the following manner :—They were stained 
with borax methylene blue, then passed into water and very quickly 
into a strong aqueous solution of eosin, finally they were dehydrated 
and mounted in balsam. 
Let us consider, for example, a transverse section from the dace 
a few days before being hatched (eight days after fertilization). 
Under a very slight magnifying-power we perceive, it may be in the 
nerve-centres or in the masses of mesoblast, blue spots, which form 
a contrast with the ground-colour of the section, which is distinctly 
of a reddish hue. Under a sufficiently high magnifying-power we ~ 
discover that these blue spots are beautiful karyokinetic figures, the 
chromatin of which exhibits in all the stages a very delicate affinity 
for the methylene blue. The granulations of the resting nucleus‘ 
are stained by the eosin: only one or two granules, which are 
clearly indicated, react like the chromatic portions of the figures of 
division, and may be regarded as nucleoli. Two important conclu- 
sions result from these observations :— 
1. Methylene blue is, under these conditions, a genuine reagent for 
chromatin in an active state. 
2. With the exception of the nucleolus or nucleoli, the granulations 
of the resting nucleus have not the same reaction as the chromatin of 
division; their chemtcal composition must therefore undergo a change 
when they become constituent parts of the filament. 
We would remark that if the action of the eosin is too prolonged, 
or if the decoloration with alcohol is pushed too far, the blue tint 
will entirely disappear. Here we have a device of preparation, 
But since the results of this device are constant for the various stages, 
in numerous sections and in different tissues, it must correspond to 
a constant condition. The method indicated seems to us to be of 
value for the technique of cytology, which is, moreover, made up of 
devices. 
Results.—Let us apply this method to the study of division in the 
first stages of development. During the whole of the first day the 
blastoderm-spheres, which multiply rapidly, exhibit all the stages 
of indirect division. In these cells we observe the rays of the asters 
extending from the periphery of the nucleus to the membrane 
throughout the whole mass of the protoplasm. These asters are 
either simple or double ; all the stages in the division of the centro- 
somes and their migration towards the poles are easily followed. 
Until the moment when the spindles appear the nuclei look like 
clear areole bounded by a delicate membrane ; not only are the few 
