476 



CHARLES RUSSELL BARDEEN 



65 per cent after abnormal development died early in the period 

 of larval differentiation, and 30 per cent died in the later periods 

 of larval differentiation. None developed into free swimming 

 tadpoles and none lived beyond the eighth day after fertilization. 

 In the groups subsequently exposed all specimens showed some 

 larval differentiation and a successively greater number developed 

 apparently normally until the latter part of larval differentiation. 

 In Experiment B-21|, exposure from twenty-one and one-half 

 to twenty-two and one-quarter hours after fertilization, 6 per 

 cent of the eggs developed into free swimming tadpoles but none 

 of those lived longer than two weeks; in Experiment B-22|, 

 exposure from twenty-two and one-half to twenty-three and one- 

 fourth hours after fertilization, 16.7 per cent developed into free 

 swimming tadpoles; in Experiment B-26, exposure from twenty- 

 six to twenty-six and three quarter hours after fertilization, 35 . 3 



TABLE 6. 



Irradiation at stages from advanced cleavage to closure of blastopore. 



Experiment A 



