454 CHARLES RUSSELL BARDEEN 



per cent became abnormal during larval differentiation. Com- 

 paratively few of the abnormal larvse in these experiments, how- 

 ever, exhibited the relatively advanced degree of differentiation 

 attained by the majority of the abnormal forms in the sperm 

 experiments. The types of abnormalities appear to be not es- 

 sentially different in the later larval stages in the two sets of exper- 

 iments. 



5. Tadpole period 



In Experiment 6, 2.7 per cent reached the definite tadpole 

 stage and of these only a ninth (0 . 3 per cent of the total number 

 of eggs fertilized) developed as normal tadpoles. In Experiment 

 7, 1 . 7 per cent of the ova fertilized became definite tadpoles but 

 none of these lived long. In Experiments 4 and 5, 4.2 per cent 

 and 5 . 1 per cent respectively became apparently normal tadpoles. 

 None of those in Experiment 4, however, lived more than a few 

 weeks while some of those in Experiment 5 were followed to 

 metamorphosis. In Experiments 1-3 a considerable percentage 

 of organisms reached the tadpole stage and developed normally. 



COMPARISON OF THE RESULTS OF EXPOSURE OF SPERMATOZOA 



AND OF MATURE OVA 



A comparison of Experiments 1, 2 and 3, table 2, with Experi- 

 ments 1, 2, 3, 4, 7, and 8, table 1, shows quite clearly that the 

 effects of exposing spermatozoa in water for from twelve to forty- 

 five minutes are more marked than when ova within the toad or 

 frog are exposed for similar periods of time to rays of similar 

 intensity. On the other hstnd, exposure of male frogs to weak 

 rays seems to have less effect on the spermatozoa than exposure 

 of female frogs has on the ova. (Experiments described on page 

 456.) 



The number of fertilized ova which become tadpoles is approxi- 

 mately equal when sperm or ova are exposed for an hour or more 

 to intense rays, but the effects are noticeable earlier in develop- 

 ment and are more profound in the experiments with ova han 

 in those with the sperm. The injurious effects of exposed sperm 



