344 A - w - BELLAMY. 



the egg and parallel to the floor of the segmentation cavity. It 

 is characteristic of strongly inhibited eggs that the gastrular 

 angle approaches and often equals o. Not infrequently the angle 

 becomes negative, i.e., a circular blastopore is formed above the 

 equator. Some of the experiments where this shifting of the 

 point of appearance of the blastopore occurred have been cited 

 (PP- 337 339> 34o)- Several variations of this modification are 

 illustrated in Fig. 21. 



Under conditions where marked acceleration of development 

 occurs, e.g., in w/ioo,ooo KNC; /5,ooo to n/ 20,000 HC1 6 (2 c.c. 



eye 



FIG. 23. ,4, normal. B, microcephalic, eyes closer together than normal, 

 nasal pits fused, ventral suckers absent. Three hours' exposure (from early 

 gastrula) to m'n LiCl; 13 days in water. (Experiment R 122.1.) 



to 5 c.c. of n;io HC1 in well water) made up in well water, there 

 is a tendency for the gastrular angle to approximate 45 or even 

 50. It is much more difficult to alter the space relation of the 

 blastopore and apical region by acceleration than by inhibition. 

 It may be noted that the effects of acceleration become more 

 apparent about the time of hatching. In these cases the embryos 

 are markedly jnacrocephalic and dorsally convex, indicating more 

 rapid growth of the anterior and dorsal parts. 



C. Differential Inhibition in Later Development. The whole 

 problem of differential susceptibility involves of course, not only 

 differential inhibition, with which this paper is primarily con- 

 cerned, but it also includes differential acclimation and recovery, 



6 I am aware that acid is generally regarded as an inhibitor of protoplasmic 

 activity, but in these experiments the acceleration of development in certain con- 

 centrations of HC1 is perfectly definite and distinct. Similar results were obtained 

 independently and repeatedly by both Dr. Child and myself. Since the well water 

 in which the solutions were made up contains various salts and other substances in 

 minute amounts it remains to be decided whether the acceleration of development 

 in these cases is a direct or an indirect effect of the acid. 



