28 DUBLIN 



been able to make out the longitudinal split in these dyads, 

 which undoubtedly exists. In the excessive elongation of the 

 structures during the division process the two sister portions 

 have simply come into more intimate relation, thus giving to 

 the products of the division the appearance of homogeneous 

 knobs drawn out into a blunt end in the direction of the 

 equator. 



Owing very probably to the rapidity with which the later 

 stages of this division are passed through, I have not found 

 among my many preparations any stages between these ana- 

 phases and the late telophases. By this time the spindle has 

 advanced even further toward the periphery, and the first polar 

 body is extruded. This structure is a comparatively large 

 sphere in which lie the eleven chromosomes, now much con- 

 centrated. At this stage these may be quadrupartite, spherical, 

 or even rod-like in structure, showing in this last instance a 

 very distinct constriction at the middle. This, preserved plainly 

 in the chromosomes of this form, represents the points of union 

 of the sister univalents which had arisen through the longitu- 

 dinal split in the early growth stages. As these chromosomes 

 later move apart in preparation for the division of the first polar 

 body, they show clearly bands of linin connecting them through- 

 out. In striking contrast with the egg, also, the polar body is 

 of pure cytoplasmic substance in which no yolk spheres are to 

 be found. 



The first division completed, the chromosomes within the egg 

 very probably persist individually in the telophase without 

 forming a resting nucleus. The centrosome and aster also 

 divide very rapidly, forming the beginnings of a new spindle, 

 the long axis of which is%t first 90° to that of the preceding 

 one (Fig. 96). The chromosomes are distributed irregularly 

 over the whole of one side of the spindle, and are of the same 

 form as just described for their sister chromosomes of the first 

 polar body. In addition, however, there are also present a few 

 of distinctly U shape, the arms of which are rather close 

 together. The bend of the U would, in these, correspond to 

 the constrictions at the middle points of the bar shaped chromo- 



