332 A. W. BELLAMY. 



pole and the germ ring) is greater and proceeds most rapidly in 

 the sagittal plane. The significance of this process is discussed 

 elsewhere (p. 349). 



A. Disturbances in Cleavage such that the Egg Never Gastndates. 

 (a) Cell Size Ratios. In frog eggs so strongly inhibited that 

 they do not gastrulate, cleavage usually begins and proceeds 

 more or less normally for several hours. The rate of cleavage 

 in the animal hemisphere then becomes less and less rapid, 



FIG. 14. Y-shaped blastophore, .4; Equatorial gastrulation, B; Secondary 

 invaginatiori, C. Produced in z/5oo,ooo HgCls. About 40 per cent, of the eggs 

 showed the Y-shaped blastophore. (Experiment IV 70.) 



relatively, until the cell size ratio approaches and may become 

 equal to one (10/10, Fig. 10, B), whereas this ratio in a normal 

 egg of a comparable stage of development is about 3.5/10 to 

 4/10 (Fig. 10, A). 



The cleavage ratio was found to increase in value consistently 

 in all cases 1 where inhibition was sufficient to prevent the com- 



1 This distortion of the cleavage ratio was obtained in: Experiments KNC A i; 

 H i; exposure 12 hours in ?K/I,OOO from 2-cell stage; cl. = 5/10 to 7/1.0. Experi- 

 ment KNC C.?; exposure 24 hours in ?/2,ooo from 2-4-cell stage; cl. = 7/10. 

 Experiment KNC C.8; 48 hours exposure to z/2,ooo from 2-cell stage; cl. = 8/10. 

 Experiment KNC C.I2; 48 hours exposure to m/2,ooo from 2-cell stage; cl. 

 = 7/10 to lo/io. Experiment KNC C i; 12 hours exposure to ml 5,000 from 

 2-cell stage; cl. = 5/10 to 6/10. Experiment KNC C.6; 24 hours exposure from 

 2-4-cell stage; cl. = 5/10 to 7/10. Experiment KNC C.Q; 5 days exposure to 

 wz/io,ooo from 2 cell-stage; eggs beginning gastrulation (equatorial) with 6/10 to 

 8/10 cl. Experiment IV 21; 21 1/2 hours exposure to m/8.$ LiCl from an unseg- 

 mented stage; in about 15 per cent, to 20 per cent. cl. = 4/10-7/10. Experiment 

 IV 31; unsegmented eggs exposed 4'hours in m/4 LiCl, then 7 1/2 hours in water 

 showed an 8/10 to 10/10 cleavage ratio. Experiment IV 54; eggs in late cleavage 

 exposed 40 hours to m 1 100,000 NgCh; cl. = 6/10 to 10/10. Experiment IV 62; 

 eggs in 4-8-cell stage exposed 12 hours in 0.0075 per cent, formaldehyde; cl. = 6/10 

 to 10/10. Citations of experiments in italics are from Dr. Child's preserved 

 material, "cl." = cleavage ratio. . 



