632 J-- ß- Cary. 



In the anaphase of the maturation divisions the daughter plates 

 are drawn apart so that the one which is to remain in the nucleus 

 comes to lie in the centre of that bodj^; while the one which is to 

 be extruded into the polar body goes to the extreme end of the 

 nucleus where the latter is in apposition to the cell wall. The 

 earliest stages in the extrusion of a polar bodj^ I have been unable 

 to find in an}' of nn^naterial. lu a later stage as shown in Fig. 38 

 the interior of the polar body is continuous witli that of the nucleus 

 through a rather broad stalk. In this stage the chromosomes in 

 both of the daugliter plates still retain their individuality, and, 

 indeed, have not been drawn up to form a close cluster, so it seems 

 probable that in this instance we have to do with a comparative!}' 

 early stage in the process. 



In the egg represented in Fig. 39, there is still a ver}' narrow 

 connection between the polar body and the nucleus. The chromosomes 

 of each daughter plate have, for the most part, lost their identity. 

 They form a homogeneous mass which shows only about the outer 

 border any trace of its origin from separate chromosomes. From 

 the evidence given in the last mentioned figure it would seem that just 

 as in the segmentation divisions, the constriction of the nucleus to 

 cut off the polar body is a comparatively slow process. The 

 separation of the polar body becomes complete only after the 

 chromosomes in both daughter plates have become indistinguishable 

 from one another. In the nucleus of the ripened egg they have 

 fused to form the caryosome; in the polar body, on the other hand, 

 there is never a sharply defined body comparable to the caryosome, 

 but the chromatin material becomes scattered throughout the 

 nucleoplasm in the form of irregular granules. At first these 

 granules are distinct from one another. Later the whole mass of 

 the polar body has a uniform staining reaction, as if the chromatin 

 material was evenly distributed, as in a solution. 



At no time in the formation of the polar body, at least in no 

 stage later than the earliest one that I have found (Fig. 38), is 

 there any evidence that the polar body contains other than nuclear 

 material. In Figs. 38 and 39 it will be seen that the membrane 

 which forms the wall of the polar body is a direct continuation of 

 the nuclear membrane. It seems probable, also, that the separation 

 of the polar body is accomplished in the same manner as that of 

 the daughter nuclei in a segmentation cell: i. e, by the fusing of 

 the nuclear membrane when the two sides come together, at the 



