ARTIFICIAL PARTHENOGENESIS IN CUMINGIA 33 



hour. The highest percentage of polar body formation is ob- 

 tained when they are exposed to 37°C. for 1§ minutes. 



3. By isolating eggs without polar bodies and observing their 

 development, it is found that they may form fairly normal 

 swimming larvae. Those with polar bodies form non-cellular 

 swimmers, if they develop at all. 



4. Cytological study of eggs which have not formed polar 

 bodies shows that the chromosomes of the first polar spindle 

 divide, and two nuclei are formed which fuse to form a cleavage 

 nucleus. 



5. In the cleavage of these eggs there are fifty or sixty small 

 rods of chromatin, instead of the thirty-six threads found in 

 the normal egg. Cleavage often follows the normal pattern 

 very closely. 



6. The chromosomes of the second polar spindle may also 

 divide and form two nuclei which fuse. Very few of the eggs 

 with one polar body divide. 



7. Eggs with two polar bodies may, in rare instances, divide 

 once or twice. Eighteen chromosomes (the haploid number) 

 are found in such eggs. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 22, NO. 1 



