Plate II 

 All figures are from sections, except 15 and 16 



Fig. 1 5 Optical section of living, abnormal blastula which was cylindrical in form and open at both 

 ends. 



Fig. 16 Egg showing amoeboid activity after treatment with acidulated water. 



Fig. 17 Simultaneous appearance of the two asters, with centrioles, on wall of germinal vesicle. 



Fig. 18 Breaking down of germinal vesicle and formation of first maturation spindle; the centro- 

 somes are double and the fibers passing to chromosomes are thicker than rest. 



Figs.ig-20 First maturation spindles, fully formed, thelatter in its definitive position; the chromosomes 

 (tetrads) are in the form of crosses, in some of which the perpendicular split may be seen. 



Fig. 21 Formation of second maturation spindle; dyads are seen in both the egg and the first polar 

 body; two centrioles with a few delicate rays are present in latter. 



Fig. 22 Second polar spindle in definitive position; the dyads are in the equatorial plane with the 

 longer axis lying transversely to the spindle. 



Fig. 23 Anaphase of second polar mitosis; the inner centrosome is double. The first polar body 

 shows mitotic activity. 



Fig. 24 Close of second maturation mitosis, showing 12 single chromosomes in egg. as well as 

 several similar chromosomes in the second polar body. 



Fig. 25 Chromosomal vesicles partially fused to form the egg nucleus; centrosomes and rays have 

 totally disappeared. 



Fig. 26 Egg nucleus during the "pause." 



Fig. 27 Simultaneous appearance of the two cleavage asters with their centrosomes on opposite 

 sides of the egg nucleus. 



Fig. 28 Fully formed, first cleavage figure; the large, reticulated centrospheres contain divided 

 centrosomes, and the spireme is segmenting into chromosomes. 



