SUSCEPTIBILITY OF AMPHIBIAN OVA TO X-RAYS 



451 



TABLE 2 

 Exposure of ovum before fertilization 



Figures in brackets indicate percentage of eggs discarded because of lack of 

 fertilization. 



The internal effects have been studied chiefly in the toad eggs 

 of Experiment 6 and the following account is based mainly upon 

 that study, but the results reported have been confirmed by a 

 study of the frog eggs of Experiment 7. 



1 . Fertilization 



In all of the experiments there were a few eggs not fertilized 

 but the percentage of unfertilized eggs was large merely in Exper- 

 iment 6 where it reached about twenty per cent. In this experi- 

 ment the large number of eggs used and the difficulty of mixing 

 quickly so large a number of eggs with the sperm emulsion prob- 

 ably account for the unfertilized eggs. Experiment 7, in which 

 but one out of one hundred and seventy-eight eggs was not fer- 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 11, NO. 4. 



