GERM CELLS OF COELENTERATES 603 



growth, and in the older gonads all of the larger oocytes have 

 this appearance, with the germinal vesicle large and sharply 

 marked and the chromatin rather uniformly distributed along 

 the reticulum. As the time of the maturation mitoses ap- 

 proaches, the chromatin of the reticulum draws into masses 

 (fig. 12) which gradually condense to form the haploid number 

 of chromosomes, the nuclear membrane disappears, the chromo- 

 somes which have assumed their definitive shape are set free 

 (fig. 13), the spindle forms and the chromosomes enter the 

 spindle. Figures 12 to 14 show that there is an excess of chro- 

 matin in the nucleus not used for making the chromosomes and 

 this is set free in the cytoplasm and dissolved, along with that 

 which earlier left the nucleus. Before the chromosomes enter 

 the equatorial plate they may show indications of splitting (fig. 

 13) preparatory to their separation in the anaphase. 



In the formation of the polar bodies there is nothing unusual 

 nor especially noteworthy except the very large size of the 

 chromosomes and the remarkable clearness of the various phases 

 of the process. It seems possible that the process of polar body 

 formation goes on slowly, for the different phases were extremely 

 common and were found in hundreds of eggs within the gonads. 

 In the first maturation spindle there are no asters and no centro- 

 somes or attraction spheres, the spindle being rather barrel- 

 shaped. The chromosomes vary in the forms assumed during 

 the anaphase of division, showing rings, dumb-bells, crosses; 

 probably all of these are expressions of differences in the attach- 

 ment of spindle fibers and in the way the chromosomes are pulled 

 apart. Figures 19 to 24 show some of the phases of division 

 seen in the first maturation mitosis. There is some variation in 

 the time of separation of the chromosomes, which may result 

 in a delayed division of some of the chromosomes (fig. 14). 



The polar body is rather large and contains eight chromo- 

 somes, which is the number retained in the egg. The chromo- 

 somes which remain in the egg draw together into a group (figs. 

 15, 16, 28, 29) which produces a vacuolation of the cytoplasm, 

 perhaps forming several vesicular vacuoles each enclosing one or 

 more of the chromosomes. There is never the formation of a 



