566 



CELL DIVISION IN EGGS OF CREPIDULA. 



V. Effect of Abnormal Temperature. (Continued.) 



1.175 (1) 



(2) 



1.176 (1) 



(2) 



1-8 cells. 



1-8 cells. 

 4-16 cells. 



(2) 



4-16 cells. 



(3) 



4-16 cells. 



(4) 



4-16 cells. 



(5) 



4-16 cells. 



1,177 (1) 



1-2 cells. 



1-2 cells. 



Experiment. 



33° 



r 33° 



L Ca. 27°* 

 34°-35° 



J" 34°-35° 

 t Ca. 23°* 



' 34°-35° 



. Ca. 22°-25°< 



" 34°-35° 

 . Ca. 22°-25°* 



' 34°-35° 

 _ Ca. 22°-25°* 



33°-34° 



f 33°-34° 

 1 Ca. 22°-25°* 



thr. 



ihr. \ 

 3 hrs. J 



ihr. 



irs. J 



3hrs. 



Ihr. 1 

 19 hrs. J* 



ihr. 

 27 hrs. 



,} 



Ihr. I 

 44 hrs. J 



Jhr. 



ihr. \ 

 irs. J 



17 hrs. 



Orientiaton of mitotic figure changed; spindle 

 fibers gone; chromosomes scattered, otherwise 

 normal in appearance. 



Irregular cleavages, due to reduced surface 

 tension; many karyomeres, due to scattered 

 chromosomes; mitosis normal at 27°. 



Sharp segregation of cytoplasm and yolk; archi- 

 plasm drawn into central areas and division 

 walls; chromosomes scattered; centrosome and 

 spheres indistinct. 



Collection of clear plasma at animal pole and 

 along cleavage furrows; cleavage frequently 

 suppressed; many karyomeres and irregular 

 nuclei, each with a large nucleolus. 



Ca. 24-30 cells; cleavages nearly normal, though 

 sometimes suppressed; many scattered chromo- 

 somes and karyomeres. 



Ca. 52-60 cells; similar to preceding; chromatic 

 connections between daughter nuclei, the result 

 of scattered chromosomes. 



Ca. 80-^90 cells; many karyomeres and irregular 

 nuclei which persist through many mitoses but 

 do not interfere with regular cleavages. 



Daughter nuclei and clear plasma drawn down 

 into middle of egg along cleavage furrow; latter 

 often suppressed at vegetal pole and not at 

 animal; some scattered chromosomes. 



Ca. 30-40 cells; second cleavage may be sup- 

 pressed, and polyasters may be present; many 

 karyomeres, especially in entomeres. 



* Room Temperature. 



