No. 



849 



850 



851 



852 



853 



854 



884 



885 



886 



893 



894 



895 



896 



897 



898 



899 



900 



901 



902 



903 



904 



905 



906 





907 



908 



909 



CELL DIVISION IN EGGS OF CREPIDULA. 



561 



III. Effects of Pressure. 



Stage. 



1-2 cells 



Experiment. 



Pressed between 

 slides. 



Duration. 



1-4 cells. Pressed between 



4 hrs. 



Free 

 in Sea 

 Water. 



Bwriu. 



13 hre. 



lcell. 



slides. 



Pressed between 

 slides. 



5J hrs 



6 hrs. 



1&-30 cells; many abnormal 



cleavage being incit 



8 hre 



13 hrs 



2-4 cells. (Pressed between 



slides. 



1-4 cells. Pressed between} 14 J hrs 



glasses. 



between 18 hrs. 



axis of pressure, i— ^ , «w 



2-24 cells; many cleavafes iboormal b siss 

 and direction; yolk cleara* a*? bt 

 increased or nip pressed. 



1-4 cells 



cover 

 Pressed 



1-2 cells. 



cover glasses. 

 Pressed flat 



under 

 1-2 cells. I Pressed 



slides. 



cover, 

 between 



4 cells. Pressed between 



slides. 



24 cells. [Pressed between 



slides. 

 Pressed between 



3i hrs. 

 4 hrs. 



lcell. 



slides. 



4 cells. [Pressed out 



capsules. 



of 



12 J hrs. 

 4 hrs. 



4 hrs. 



30-40 cells. Pressed in cap- 



lcell. 



16-24 cells. 



1&-24 cells. 



1-24 cells. 



1 cell. 



4^16 cells. 



1 cell. 



1-8 cells. 



1 cell. 



1-8 cells. 



sules. 



Pressed out of 

 capsules. 



Pressed in cap- 

 sules. 



Pressed in cap- 

 sules. 



Pressed out of 

 capsules. 



Pressed out of 

 capsules. 



Pressed out of 



4 hrs. 



4 hrs. 



4 hrs. 



4 hrs. 



4 hrs. 



capsules. 



Pressed 



out of 



4 hrs. 



4 hrs. 



4 hrs. 



4 hrs. 



capsules. 

 Pressed in cap- 



sules. 



Pressed 



out of 



4 hrs 



4 hrs 



lcell. 



capsules. 



Pressed out 

 capsules. 



Pressed out 



capsules. 



of 4 hrs. 



of 4 hrs. 



1-24 cells. Pressed out of 



8-24 cells. 



capsules. 

 Pressed in cap- 

 sules. 



4 hrs. 



4 hrs. 



11 hrs. 20-24 cells; 1, 2, or many mctomm 



suppression or mem 



to 



4 hrs. 



3 hrs. 



4 hrs. 



12J hre. 

 101 hrs. 



1J hrs. 



Jhr. 



ihr. 



thr. 

 2 hrs. 



Jhr. 

 2 hrs. 



hrs. 



hrs. 



hrs. 



2 hrs. 



2 hrs. 



2 hrs. 



2 hrs. 



2 hrs. 





2 hrs. 

 4 hrs. 



4 



Of folk ofea 



polyasters and multiple racM. 

 8-30 cells; similar to pr» 'I 



meres isolated 



4-30 cells; many normal qgp; abooobal forma 

 like those in Xo. 862. 



1-30 cells; in soma in all issnp sup- 

 pressed; others show abnormal forma afasAar 

 to preceding. 



1-30 cells; many isolated hlastomans, fraj? 

 mented and degenerating cpja. 



20-30 cells; yolk cleavage suppressed (with 

 multiple nuclei) or increased (with multi- 

 plication of macromcrea). 



Many fragmented and degenerating: 

 mal cleavages similar to j receding. 



Few modifications. 



1-2 cells; few modification* 

 Few eggs; few modification* 

 Few modifications; egfp faded. 



Few eggs and much f 



Ca. 30 cells; few modifications. 



Illl 



24-30 cells; eggs packed together and ■hnocmal 



in form. 

 1-24 cells; macromeres may lie abnormal in 



number, rise and position. 

 1-4 cells; modifications similar to prooed 



Fig. 48. 

 4-20 cells; similar to No. 900. 



1-4 cells; modifications similar to No. 900, 



1 



1 



16 cells; macromeres »d micromeres may 

 be abnormal in number, site and position* 



Fig. 55. 



•8 macromeres; few 



. t'A 



1-20 cell*; a few abnormal cleavage form! 



Fig. 30. , , .. . 



1-4 cells; unequal and non-synchronous an; 



dons of macromerea. 

 1-30 cells: exovatei on some macromcrea. 



hrs. 30-40 cells ; almost all normal. 



37 JOURN. ACAD. NAT. SCI. PHILA. VOL. XV. 



