334 WILSON AND MATHEWS. [Vol. X. 



granules appears before the other, and migrates some distance 

 from the nucleus before the second appears. In cases where 

 they both lie clearly outside of the nucleus, the nuclear mem- 

 brane is invariably broken behind them. Although similar 

 granules may be seen within the vesicle, they cannot be identi- 

 fied as centrosomes, if they be such, on account of the lack of 

 archoplasm or radiations about them. 



When the granules first appear the archoplasm surrounds 

 them as a faint and minute halo. At a little later stage, how- 

 ever, it becomes clearly distinct (see Fig. 5, A), and, as the 

 centrosomes move outward from the nuclear wall, it rapidly 

 grows, while radiations appear about it. The archoplasm-mass 

 divides into two portions, with a centrosome in each (see Fig. 

 5, B), and these gradually move apart as a central spindle 

 develops. The amphiaster now lies tangentially along the top 

 of the nucleus. The nuclear wall has already disappeared in 

 this vicinity; astral rays grow down into the nucleus; and cer- 

 tain irregular agglomerations of chromatin lying at the upper 

 part of the germinal vesicle pass into the position of the equa- 

 torial plate of the spindle. (One constituent of the chromatin, 

 by far the larger part, is converted into cytoplasm. No per- 

 sistence of chromosomes occurs.) The spindle then rotates 

 and takes up a radial position. At this time the single centro- 

 some has divided into two or three minute granules lying in a 

 spherical archoplasm which stains a bright vermilion in Congo 

 red (see Fig, 5, Q. 



The chromatic masses of the spindle now arrange themselves 

 into seventeen (.?) double (quadruple .?) chromosomes. The first 

 polar body carries with it seventeen (.■') double chromosomes 

 and one of the asters. The outer centrosome of the second 

 polar spindle is formed at the " Zwischenkorper " of the first, 

 and the second polar body removes this and seventeen Q) single 

 chromosomes, leaving in the ^g^ an archoplasm containing one 

 or two minute centrosomes and seventeen (.?) single chromo- 

 somes. The egg-nucleus re-forms, as described by Hertwig 

 and Fol, as a group of four or five little vesicles, which later 

 fuse into one (see Fig. 5, D). The centrosomes disappear 

 during this process, and the archoplasmic rays, which persist 



