570 CELL DIVISION IN EGGS OF CREPIDULA. 



IX. Effects of Diluting Sea Water with Fresh Water. 



Dilution. 



Dilute. Normal. 



Kesults. 



870 

 871 



873 



874 

 875 



964 

 955 

 956 



993 (1) 



(2) 

 (3) 



1,182 (1) 



2-4 cells. 



2-4 cells. 



lcell. 

 1-4 cells. 



lcell. 



lcell. 



4-20 cells. 

 1-8 cells. 



4-8 cells. 



2-20 cells. 

 2-20 cells. 

 2-20 cells. 



1-4 cells. 



1-4 cells. 

 1-4 cells. 



1-4 cells. 



1-4 cells. 

 1-4 cells. 



lpart 



lpart 



2hrs. 



lhr. 



ihr. 

 lhr. 



ihr. 



ihr. 



lhr. 

 Ihr. 



ihr. 



3hrs. 

 3hrs. 

 2hrs. 



lfhrs. 



If hrs. 

 lfhrs. 



2 hrs. 

 2 hrs. 



14 hrs. 



4 hrs. 



lihrs. 

 12 hrs. 



15 hrs. 



24 hrs. 



25 hrs. 

 7 hrs. 



20 hrs. 



Ohrs. 

 14 hrs. 

 36 hrs. 



1BJ hrs. 



Ohrs. 

 27 hrs. 



Ohrs. 



18 hrs. 

 28 hrs. 



24-30 cells; yolk cleavage sometimes suppressed, 

 polyasters, multiple nuclei; chromosomes may be 

 scattered along spindle and form chromatic con- 

 nection between daughter nuclei; older stages 

 normal, or nearly so. Figs. 145, 147, 152, 153, 

 154, 157, 158. 



Many eggs bursted and chromatin of nuclei dis- 

 solved; no separation between yolk and cyto- 

 plasm; chromatic connection between daughter 

 nuclei; nucleoli large. Fig. 141. 



1-2 cells; few abnormalities. 



L— 30 cells; many isolated macromeres showing par- 

 tial cleavage; blastomeres may be abnormal in size, 

 position and quality; yolk cleavage often sup- 

 pressed; polyasters and multiple nuclei. Fig. 156. 



1-25 cells; cleavage may be adequal and little 

 difference between macromeres and micromeres; 

 yolk cleavage increased; direction of cleavage may 

 be modified; spindles may be degenerate and con- 

 nective fibers chromatic. Figs. 136, 142, 143. 



Similar to preceding; many eggs fragmented and 

 degenerate. 



Ca. 52 cells; a few partial eggs, others normal. 



1-24 cells; isolated macromeres; in some cases yolk 

 cleavage suppressed, in others increased; 1-many 

 macromeres; polyasters, degenerate spindles, 

 multiple spheres; tendency to equal cleavage of 

 yolk; enormous polar body. Figs. 39, 132-135, 

 137-140, 144. 



24-32 cells, many normal, others fragmented; chro- 

 matic connection between daughter nuclei. 



Few eggs, showing few abnormalities. 



Similar to preceding. 



Ca. 68 cells; many show polyasters, abnormal 

 distribution of chromosomes, multiple nuclei. 

 Fig. 150. 



24-42 cells; in some eggs yolk cleavage suppressed 

 with formation of polyasters, karyomeres, and 

 multiple nuclei; in others yolk cleavage increased. 

 Figs. 146, 148, 149, 151, 155. 



1-4 cells; some isolated blastomeres; chromosomes 

 scattered; position and direction of spindles 

 changed. 



Ca. 52 cells; irregular cleavage; yolk cleavage may 

 be suppressed, giving rise to polyasters, multiple 

 nuclei and discoidal cleavage, or it may be 

 increased, macromeres and micromeres becoming 

 equal in size. 



1-4 cells; no sharp distinction between yolk and 

 cytoplasm; many yolk spheres have escaped 

 through cell membrane; lobes and deep furrows 

 at animal pole; large polar bodies; nuclei large, 

 centrosomes and spheres small and dense; 

 scattered chromosomes and karyomeres; cleav- 

 ages may be suppressed and nuclei displaced and 

 macromeres separated. 



16-52 cells; many normal, others very abnormal, 

 with equatorial and meroblastic cleavages, and 

 with irregular nuclei and karyomeres. 



52-70 cells; many normal, others similar to pre- 

 ceding. 



