74 W. JB. Kirhham — Maturation of the Egg of the White 3fouse. 



fully formed spindle with the chromosomes in the equatorial plate is 

 seen. Bellonci ('85) describes the first ])olar spindle in the eirgs of 

 mice and guinea-pigs as exactly like that found in the eggs of inver- 

 tebrates, and he occasionally saw faint traces of aster-fibers at the 

 ends of the spindle. The first polar spindle is formed from the 

 germinal vesicle, which, as mentioned above, is eccentrically placed 

 within the agg at the end of the spireme, and, as described by 

 Sobotta ('95) in the egg, of the mouse, and by Rubaschkin (105) in the 

 Qgg of the guinea-pig ; this spindle lies at first in a position at right 



Figure ■■). — Camera drawing of a living egg in the Fallopian tube soon after fer- 

 tilization ; showing the two differentiated layers of the zona pellucida. 

 The finely granular portion of the egg indicates the position of the pro- 

 nuclei. Both polar bodies have been retained by the egg, the larger one at 

 the right being the first polar body : around them appears a space filled 

 with fiuid. X 3:^0. 



Figure 4.— Ovarian egg ; showing first jDolar spindle in paratangential position. 

 The chromosomes are in most instances bivalent. Note centrioles at foci of 

 spindle, x 675. 



angles to the radius of the egg, and near the surface. The chro- 

 mosomes still vary greatly in size and shape, but are never filiform 

 (Text-fig. 5), and generally lie with their long axes coincident with 

 that of the spindle. The number of chromosomes in the first jjolar 

 spindle agrees with that above noted at the end of the spireme, 

 being between 12 and 24. At the foci of the first maturation spindle, 

 centrioles consisting of one or more tinj' eccentrically placed granules 

 have often been observed, and similar bodies have been seen at this 

 stage by van der Stricht (:o6) in the eggs of Vesperugo noctula. 



