568 



CELL DIVISION IN EGGS OF CREPIDULA. 



b. In Stoppered Bottles. 



1,010 1-4 cells. 



1,011 



1,012 



1,013 

 1,014 

 1,015 



1,016 



1,017 



1,018 



1,020 

 1,021 

 1,022 



lcell. 



1-4 cells. 

 2-20 cells. 

 Gastrulee. 



1-8 cells. 



1-8 cells. 



1-8 cells. 



1 cell to gas- 

 trula. 

 1-20 cells. 

 1-20 cells. 

 2-20 cells. 



36hrs. 



Ohrs. 



5 hrs. 



Ohrs. 



6hrs. 

 20 hrs. 

 20 hrs. 

 24 hrs. 



Ohrs. 

 Ohrs. 

 Ohrs. 

 Ohrs. 



27 hrs. 



Ohrs. 



48 hrs. 



Ohrs. 



48 hrs. 



Ohrs. 



20 hrs. 

 24 hrs. 

 20 hrs. 



3 hrs. 



8 hrs. 



9 hrs. 



1—4 cells; cleavage stopped; eggs smaller than normal, only 120 n in 

 diameter; nuclei large, vesicular, with large nucleoli; centrosomes 

 very large; sphere granules widely scattered. Figs. 106-109. 



1-4 cells; astral rays withdrawn and spheres very distinct; otherwise 

 typical. 



1-20 cells, nearly normal. 



2-20 cells; nuclei large, with chromatin clumped. 



No changes. 



1-30 cells (a few older stages accidentally included) ; big nuclei with 

 chromatin clumped; spindles faint. 



1-20 cells; nuclei large and achromatic; nucleoli large; sphere gran- 

 ules scattered. Figs. 112, 114. 



1-20 cells; big nuclei and nucleoli; chromatin clumped; sphere gran- 

 ules scattered. Figs. 113, 117. 



1 cell to gastrula; similar to preceding; cleavage stopped in early 

 stages, later stages not so much affected. 



2-24 cells; normal; no development while in boiled sea water. 



8-40 cells, normal; no development while in boiled sea water. 



24-52 cells; similar to preceding. 







• 



2. Partial Atmosphere of Hydrogen. 



No. 



Stage. 



Hydrogen 

 Stream. 



Closed 

 Bottle. 



Open 

 Bottle. 



Results. 



879 



1-40 cells. 



3 hrs. 







1-40 cells; nuclei of older stages normal; of earlier 

 stages, large, achromatic, with large nucleoli. 



880 



1-30 cells. 



4} hrs. 







1-30 cells; same as preceding. 



881 



1-30 cells. 



Control. 





4} hrs. 



4-48 cells, normal. 



882 



1-30 cells. 



7J hrs. 







1-30 cells; same as No. 879. 



883 



1-30 cells. 



Control. 





7ihrs. 



24-52 cells, normal. 



1,023 



2-20 cells. 



2 hrs. 





2 hrs. 



2-24 cells; nuclei and nucleoli large, chromatin clumped; 

 few polyasters; centrosomes and spindles distinct. 

 Fig. 115. 



1,024 



2-20 cells.* 



f 2 hrs. 

 1 1 hr. 



18 hrs. 



3 hrs. 



2-24 cells; similar to preceding; centrosomes and 

 spindles unusually distinct. 



1,025 



2-20 cells.* 



f 1 hr. 

 1 lhr. 



18 hrs. 



3 hrs. 



2-24 cells; similar to preceding. Figs. 110, 111, 117, 

 118. 



1,026 



2-20 cells.* 



f lhr. 

 1 lhr. 





5 hrs. 



No development while in hydrogen; after 20 hrs. in 



20 hrs. 





fresh sea water eggs had reached 48-86 cells. 



1,027 



1-20 cells. 









1,028 



H 60%— Air 40% 



2-4 ceUs. 

 H 70%— Air 30% 



12 hrs. 





1-20 cells; cleavage stopped; nuclei nearly normal. 



12 hrs. 





2-4 cells; cleavage stopped. 



1,029 



1-20 cells. 











H 70%— Air 30% 



24 hrs. 





1-20 cells; similar to preceding. 



* Eggs from two experiments mounted together. 







3. Stoppered Bottles of Normal Sea Water. 



No. 



Stage. 



Duration. 



Results. 



941 



946 

 1,019 



2-8 cells. 



1-8 cells. 

 1-20 cells. 



20 days. 



20 days. 

 48 hrs. 



4 cells to veliger; in early stages, division may be permanently halted 

 in metaphase and anaphase; framboisia; exogastruke. 



Same as preceding. 



1-30 cells; cleavage checked; nuclei large and clear, with chromatin 

 clumped, as in boiled sea water. 



