DIFFERENTIAL DEVELOPMENTAL MODIFICATION. Ill 261 



Neurula stages with relatively slight inhibition show reduction of the 

 anterior part of the neural plate and often a permanently open blastopore 



B 



D 



vs 



Fig. 106, A-F. — More advanced stages of differential modifications of frog development. 

 A-E, differential inhibition. A, KCN, 4 days from two-cell stage, water 2 days; B, formalde- 

 hyde 0.0075 per cent, 2 days from four- to eight-cell stage; C, microcephalic with shallow neural 

 groove and persistent yolk plug, KCN m/5,000, 24 hr., water 5 days; D, KCN m/io,ooo, 4 

 days, water 8 days; forms like A-D also obtained with LiCl; E, fused suckers and nasal pits, 

 tail dorsiventrally differentially inhibited, LiCl m/s, 3 hr. at late cleavage, water 4 days; F, 

 differential recovery, LiCl m/io, 2 days, water 5 days, t, tail; 11 s, ventral sucker; y.p., yolk 

 plug (A-D from Bellamy, 1922; E, F, from Bellamy, 1919). 



varying in size. With increasing inhibition these characteristics become 

 increasingly conspicuous (Fig. 106, A-C). With further development neu- 

 ral folds may fail to close posteriorly and be separated by the open 



