Miscellaneous. 479 



the ovum in the dace. We now propose to f^ive 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 

 mnst 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 (juickly 

 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 wo 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. 31ethijlene 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 chemical comj'tosition 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 bo 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 tlie first day the 

 blastoderm-spheres, which multijdy rapidly, exhibit all the stages 

 of indirect division. In these cells we observe the rays of tlie asters 

 extending from the periphery of the nucleus to the membrano 

 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 areolas bounded by a delicate membrane ; not only are the few 



