1 62 GRACE MEDES. 



no differentiation of structure (Fig. 7). However, in sections two 

 or three micra thick, from which the color has been sufficiently 

 extracted, a careful study of the karyosphere under a high mag- 

 nification, reveals the fact that it is not a homogeneous body, 

 but is a complex mass, various parts of which react differently to 

 the stain (Fig. 8). When colored with the iron haematoxylin, 

 it appears to be composed of dark irregular masses, and between 

 them smaller areas which stain brown and appear to be of a homo- 

 geneous consistency (Fig. 8, b, c, d\ On the other hand, the 

 larger masses are of slightly granular nature and commonly 

 appear black. When the stain has been sufficiently extracted, 

 however, they become grayish, and this color argues their chro- 

 matic nature, just as the brownish color without testifies to the 

 achromatic nature of the karyosphere. 



Evidences of vacuoles within the karyosphere may likewise be 

 -seen (Fig. 8, b, c, d) in thin sections lightly stained in the same 

 manner, but their presence is shown much more clearly when in 

 addition to the iron-haernatoxylin congo-red is used (Fig. 8, 

 b, c}. These vacuoles in varying numbers may lie irregularly 

 throughout the substance of the karyosphere. 



From the growth period, the cell passes immediately into the 

 active prophase. The first indication of this stage has to do with 

 the appearance within the nucleus of the chromatic segments. 

 As in Scolopcudra licros (Blackman, 'oi), the first sign of activity 

 is a very slight change in the structure of the karyosphere (Fig. 

 8, c]. The texture of this body becomes more loose and the dis- 

 tinction between chromatin and achromatin becomes more marked 

 (Fig. 8, e]. This, however, is so slight that it would probably 

 pass unnoticed were it not for the more striking phenomena 

 which now follow. That the darker portions noted as occurring 

 in the karyosphere at an earlier stage are chromosomes, appears 

 very probable from the fact that they now seem to break off 

 separately from its mass and to be directly transformed into short, 

 thick, granular threads (Fig. 10). 



It would naturally be supposed that, as the chromosomes 

 leave, the karyosphere would become smaller, but such is 

 not the case ; even after a number of chromosomes are to be 

 seen lying in the nuclear area the karyosphere is apparently as 



