THE CELL ASTER 497 



may not straighten out. The ray-like structure of the aster 

 is difficult to distinguish in the hyaline cytoplasm at the periph- 

 eral pole as the refractive index of the hyaline protoplasm even 

 in its gel state is close to that of the rays. The rays of the 

 peripheral aster, however, very soon reach the periphery of the 

 egg. As the cell periphery is probably a protoplasmic gel it 

 and the peripheral aster form a continuous gel, firmly anchoring 

 the spindle. With the needle one may stretch the spindle (fig. 

 16) but it cannot be dislodged without causing disorganization. 



Division of the nuclear spindle is followed by a reversal of the 

 astral structure to the sol state. The sol state of the cytoplasm 

 lying immediately under the surface where the polar bodies are 

 to form is so liquid that granules pushed into it exhibit active 

 Brownian movement. On the surface at the middle of this 

 liquid region the egg bulges forming a nipple-like protuberance. 

 This occurs in such a way as to give one the impression that the 

 protuberance is due to a local weakening in the consistency 

 of the surface where an internal pressure causes cytoplasm to 

 flow out. As one of the daughter nuclei of the first maturation 

 figure lies directly under this spot, it is carried into the protuber- 

 ance which pinches off to form the first polar body. By prick- 

 ing with the needle one can so affect this surface as to cause it 

 to produce in succession five and six or even ten protuberances, 

 each being pinched off in its turn and very closely simulating 

 polar bodies. The other daughter nucleus of the first maturation 

 figure now lies free in the protoplasm (fig. 17) and can be pushed 

 about anywhere in the egg. If it be moved out of the hyahne 

 area into the granular cytoplasm and left there (fig. 18), the 

 granules immediately surrounding it gradually move away 

 until the nucleus comes to lie again in a hyaline area (fig. 19). 

 Granules, in the meantime, invade the original hyaline area until 

 it is indistinguishable from the rest of the granular cytoplasm. 

 The nucleus now elongates and migrates again towards the periph- 

 ery of the egg, astral rays reappear about its poles and, when 

 the second maturation spindle is fully formed, one finds it again 

 firmly attached to the surface of the egg. The second polar 

 body is thus produced some distance away from the first one 

 (fig. 20). 



