196 THOMAS H. BRYCE. 



Fig. 23 shows the earliest phase of the second division 

 which I have had the opportunity of observing. The asters 

 are already separate, and a bunch of fibres from each is pro- 

 jected towards the chromosomes, which are immediate!}' 

 drawn into the equator of the spindle. Thus no resting stage 

 intervenes between the two divisions. The whole figure is 

 still surrounded by the remains of the reticular or kino- 

 plasmic zone. The spindle when fully formed is slighter than 

 the first polar spindle. The central centrosome and aster 

 progressively increase in size until the condition is found as 

 in fig. 30. The astral rays are thick and fairly straight and 

 widely spreading. The behaviour of the outer centrosome 

 and the manner of protrusion of the polar body is exactly as 

 I have described for the first polar body (figs. 27 — 29). 



Fig. 33 shows the condition of the nucleus long ago de- 

 scribed by Hertwig after the extrusion of the second polar 

 body. The first stage in the reconstitution of the nucleus is 

 the formation of several small vesicles, which run together to 

 form a single vesicle which is the mature nucleus. The 

 description given of the process in the living egg is, that 

 several small vesicles appear approximately in the middle of 

 the radiations remaining in the egg. In the sections this is 

 clearly seen not to be the case, but the vesicles surround the 

 centrosome, and the astral rays are broken up into bundles 

 passing out between them. Later these all disappear, and a 

 single vesicle is left without any trace of centrosome or radia- 

 tion in its neighbourhood. 



Fig. 34 shows an interesting abnormality of the second 

 polar body. It is here very distinctly a small cell, and pre- 

 cisely the same phenomena are seen in the reconstruction of 

 the nucleus as in the egg. 



I must now refer to a series of figures which accompany 

 the constriction of the spindle in both maturation divisions. 

 Associated with the disappearance of the spindle is formed 

 the body called by Flemming the " zwischenkorpcr." This 

 plays a considerable role in spermatogenesis, but is figured 

 also in a considerable number of the descriptions of polar- 



