200 BULLETIN OF THE 



the polar globule. It should be remarked, however, that the extent of 

 this influence, as evinced in the radiate structure, is subject to consider- 

 able variations in different eggs at the same stage of development. 

 While a homogeneous area at the centre of this star is marked off at 

 times with great distinctness (Figs. 22, 25), in other cases the central 

 portion is less prominent. It may continue to present the appearance 

 previously noticed, as though originating from a few irregular and poorly 

 defined masses of nearly homogeneous substance. One side of this cen- 

 tral area is marked in a conspicuous manner, as will be seen presently, 

 when the structure of the spindle is considered. 



The latter has now become very much modified, and, by the advance 

 of the constriction, is made to assume successively different forms, until 

 at length it is like two spindles placed end to end rather than a single 

 structure. What we may call the outer spindle, i. e. the outer half of 

 the original body, which now occupies the polar globule, is less spindle- 

 shaped than the inner half. I have never been fortunate enough to see 

 its fibres converge beyond the zone of thickenings, after the constriction 

 has made its appearance at the base of the polar globule. A slight con- 

 vergence of the interzonal filaments toward a point on the distal surface 

 of the globule is, however, often observable (Figs. 22, 63). After fur- 

 ther constriction the region of thickenings appears more expanded, as in 

 Fig. 25. 



The internal half often preserves for some time a fusiform appear- 

 ance, though the theoretical apex at the centre of the stellate figure 

 has no visible connection with its fibres. It is only the trend of the 

 latter which indicates this point as coincident with the centre of the 

 star. The place of interruption in the fibres is dependent on the size 

 of the central area. 



Already at the beginning of the constriction the two lateral zones (or 

 nuclear plates) had migrated, the one to near the border of the deeper 

 " area," the other to a corresponding position relative to the refractive 

 body of the outer star. During the constriction the thickenings of the 

 former are found grouped together at the periphery of this " area," 

 in such a way as to form a circular disk rather than a ring such as 

 was observed in the earlier stages. The outer of these migrating 

 zones, on the other hand, has not diminished in circumference, but 

 ,has spread out, and still presents the annular rather than the disk- 

 like arrangement. When seen from the animal pole the spindle 

 thickenings in the polar globule (Fig. 42) consequently appear as an 

 ill-defined ring. 



