488 



CHARLES RUSSELL BARDEEN 



minute exposures show many abnormal larval forms and few 

 become well grown tadpoles. None in the experiments completed 

 metamorphosis. 



Of young larvae exposed for two hours many become abnormal 

 and die just before or soon after hatching but some undergo 

 normal development and metamorphose. 



Exposure of tadpoles for two and one-half hoars soon after 

 they begin to swim usually causes death within a month. Expo- 

 sure of tadpoles for two hours during metamorphosis usually 

 inhibits metamorphosis and causes death within a month. 



Diagram B 



Diagram B illustrates the effects of exposure of three different 

 lots of eggs, batches of which were exposed at successive inter- 

 vals of time. Lots A and B are those of Experiments A and B in 

 the tables in which the batches of eggs were exposed for forty-five 

 minutes. Lot C is that of Experiment C in which the eggs were 

 given half hour exposures. Since the external features showing 

 the effects of exposure differ at different periods it has been neces- 

 sary to plot the curves on the frequency of occurrence of different 

 abnormalities at different periods. The curves, therefore, are 

 diagrammatically illustrative rather than mathematically ace urate. 



