1897.] 



KEW YORK ACADEMY OF SCIENCES. 



389 



cavity is also seen. At this stage the 3'oke-granules are all 

 forced out to the peripheral regions of the egg, the central re- 

 gion being occupied by the very large spindles and asters. The 

 short, thick chromosomes (tetrads?) arrange themselves about 

 the equator of the spindle, whose fibers appear to fuse, forming 

 a smaller number of very thick and distinct fibers. Now the 

 spindle begins to change its position in the egg. The move- 

 ment often appears to take place principally about one spindle- 

 pole as a center, and the aster at this pole, showing, when sec- 

 tioned in certain planes, a conspicuousl}' spiral structure. As 

 the spindle moves, the resolution of the astral rays into the 



Fig. 2 



C3'toplasmic network on the side from which the motion pro- 

 ceeds can be seen. The rays often appear to leave behind them 

 for a short time a trail, which is nothing but the disintegrating 

 ray. Daring this movement the spindle undergoes a consider 

 able decrease in size. 



Finally the spindle — the first polar spindle — still in the equa- 

 torial plate stage, comes to lie radially in the egg with one pole 

 at the periphery (Fig. 3). In this figure a stage is shown in 

 which the chromosomes are beginning to divide and move to- 

 ward the poles. The centrosome at each pole divides, and, so 

 far as I have" been able to ascertain, this division may occur at 

 various angles to the spindle axis. 



This stage is the earliest found which shows a male aster. 

 The spermatozoon apparently enters at any point of the peri- 

 phery, as it is found in most various positions with regard to 

 the spindle. At first it is impossible to distinguish it from the 

 numerous 3'^olk-granules, as it is for some time unaccompanied 

 by an aster. At the stage shown in Fig. 3, or often somewhat 

 later, a small aster appears near the sperm-head, which is now a 

 dense, spherical body, but increasing in size. Notwithstanding 



