CELL DIVISION IN EGGS OF CREPIDULA. 



575 



No. 



(6) 



994 (1) 

 (2) 

 (3) 



(4) 



(5) 



1,187 (1) 



Stage. 



1-4 cells. 



1-20 cells. 

 1-20 cells. 

 1- 20 cells. 



1-20 cells. 

 1-2 cells. 

 1-2 cells. 



(2) 1-2 cells 



(3) 

 (4) 



(5) 



1-2 cells 

 1-2 cells 



1-2 cells 



No 



Stage. 



833 



834 

 835 



1-2 cells. 



841 



842 



1-2 cells. 

 1-2 cells. 



1-2 cells. 



1-4 cells. 



845 



1-4 cells. 



846 



866 



1-4 cells. 



lcell. 



867 



868 



X. Effects of Hypertonic Sea Water. — (Continued.) 



1. NaCl Added to Sea Water. 



Per 

 Cent 



1-8 cells. 



1-4 cells. 



991 



992(1) 

 (2) 



1-8 cells. 



1-8 cells. 



(3) 



1-8 cells. 



1-8 cells. 





Ti me in 



4 



1 



Per 

 Cent 



2 



3 



4 



2 



4 



2 



4 



1 



8 



8 



1 





4 



4 



4 



Solution. 

 2f hrs. 



2f hrs. 

 4 hrs. 

 4 hrs. 



Normal S. W. 



36 hrs. 



8 days 



Ohrs. 



Ohrs. 



4f hrs. 

 5 hrs. 



4 hrs. 



4 hrs. 



4 hrs. 

 4 hrs. 



36 hrs. 



Ohrs. 



Results 



hrs. 



19 hrs. 



30 hrs. 

 44 hrs. 



4-60 cells ; first and second cleavage of yolk may be 



suppressed; karyomeres, polyasters. 



Ca. 100-150 cells; nearly normal; few karyomeres. 



1-20 cells; no cleavage; cytasters; polyasters. 



1-20 cells; plasma, nuclei and spindles shrunken; no 

 cleavage ; many cytasters and polyasters. 



1-40 cells; very irregular cleavage; karyomeres, poly- 

 asters. 



1-2 cells; plasma, nuclei and spindles shrunken; 



scattered chromosomes; polyasters. 

 1-4 cells; cytasters are present during approach of 



pronuclei ; some furrows suppressed. 

 Ca. 30-40 cells; yolk cleavage may be suppressed; 



macromeres may be isolated; karyomeres. 

 Ca. 60-70 cells ; similar to preceding. 

 Ca. 80-100 cells; karyomeres or tabulated nuclei always 



occur where yolk cleavage is suppressed. 



4 hrs. 67 hrs. [Gastrula stages; similar to preceding. 



2. MgCU Added to Sea Water. 



Time in 



Solution. 



Normal S. W. 



■ 



9 hrs. 



9 hrs. 

 9 hrs. 



9 hrs. 



Results. 



5 hrs. 



9 hrs. 

 9 hrs. 



First and second cleavages of yolk suppressed ; heap 

 micromeres on unsegmented yolk; polyasters, kary 



17 hrs. 



5 hrs. 



4 hrs. 



17 hrs. 



meres; very abnormal 

 Similar to preceding. Fig 



Figs. 200 ; 



milar to preceding; many micromeres large and con- 

 tain yolk ; spindles deep in yolk. 



Yolk cleavage partially suppressed ; heap of micromerea 

 on unsegmented yolk ; polyasters, karyomeres ; chro- 

 mosomes scattered. 



Mrst and second cleavages of yolk largely suppressed ; 

 26-36 cells in eggs which had passed 4-cell stage ; heap 



16 hrs. 



micromeres; polyasters, karyomer 



Figs. 197, 218. 



4 hrs. 



16 hrs. 



14* hrs. 



fhr. 



Ohrs 



fhr. 



6} hrs 



10* hrs 



IS hrs. 



3 hrs. 



Ohrs 



lhr. 



3 hrs. 



3 hrs. 



14J hrs 



27 hrs. 



24r-36 cells in eggs which had passed 4-cell stage 



normal; if first and second cleavages suppresses 



heap of micromeres on yolk. 

 First and second yolk cleavages suppressed; heap of 



micromeres; polyasters, karyomeres; 24-36 cells of 



normal types. Figs. 214-216. 

 24 cells ; normal except that plasma and chromatin are 



shrunken a little. 

 First and second yolk cleavages suppressed ; Piasters, 

 karyomeres ; 16-24 cells in normal types. Figs. 4 1 , 



First and second cleavages suppressed ; heap of micro- 

 meres; polyasters, karyomeres; many nuclei loded, 

 constricted, double; older stages normal. 



First and second cleavages suppressed ; spmdles and 

 nuclei shrunken; ca. 24 cells of normal type. Figs. 



198 



First 'and second cleavages suppressed ; karyomeres 



due to failure of chromosomes to fuse. 

 1-2-cell stages have produced very abnormal forms, 



t^eU stages have produced normal forms with 



Similar 4 tt preceding; late stages with 64-70 cells; 

 karyomen 



