380 THEOPHILUS S. PAINTER 



Painter, T. S. 1914 The effect of carbon dioxide on the eggs of Ascaris. Proc. 



Soc. Exp. Biology and Medicine, vol. 12. 



1915 An experimental study in cleavage. Jour. Exp. Zool., vol. 18. 

 Stevens, N. M. 1909 The effect of ultra-violet light upon the developing eggs 



of Ascaris megalocephala. Arch. f. Entw.-Mech., Bd. 27. 

 ZurStrassen 1896 Embryonalentwicklungder Ascaris megalocephala. Arch. 



f. Entw.-Mech., Bd. 3. 



1906 Die Geschichte der T-Riesen von Ascaris meg. Zoologica, Heft 



40, Stuttgart. 



PLATE 1 



explanation of riGDRES 



All drawings made with camera lucida, and tV oil immersion. Figures 2b, 2c 

 and 2d are drawn at a higher magnification than the remainder of the figures. 



1 A 3-cell stage showing the separation of the A and B blastomeres. 

 2a A 2-cell stage showing the peculiar fusing which the chromatin in the Si 

 blastomeres. 



2b, 2c, 2d Detailed drawings of the fused chromatin. 



4 Showing a 4-cell stage with the A and B cells occupying abnormal positions. 



5 A 4-cell stage, normal after treatment with CO2. 



