l6 Charles Russell Bardeen 



which was kept for control, the other was exposed for from 

 one-half to two hours to powerful X-rays from a fairly hard tube. 

 At the end of the exposure I opened several females to obtain if 

 possible eggs immediately ready for laying. Several short pieces 

 of strings of eggs were placed in the control dish and others in 

 the dish which had been exposed to the rays. After fifteen to 

 twenty minutes these strings were removed and placed in large 

 dishes of water. The development of the control and the experi- 

 ment ova was then watched from day to day until it seemed likely 

 that the ova fertilized by the exposed sperm could no longer 

 survive. Specimens of the control and experiment embryos were 

 then preserved for microscopic study. 



Several of the experiments proved of negative value because 

 not even the spermatozoa of the control dish proved capable of 

 fertilizing the eggs, owing either to too great a lapse of time between 

 the removal of the sperm from the males or to a lack of sufficiently 

 ripe ova. The season was so short that only a few successful 

 experiments could be carried out but these were convincingly posi- 

 tive. All eggs fertilized by the control spermatozoa developed 

 normally. One of these was finally attacked by some parasitic 

 organisms, but even in this the tissues and organs showed micro- 

 scopically perfectly normal relations. All eggs fertilized by the 

 exposed spermatozoa, over fifty in number, developed abnormally, 

 with a single exception. This ovum developed into an appar- 

 ently normal tadpole but this tadpole died before any of its fellow 

 control tadpoles. It died at a time when it could not be imme- 

 diately preserved for microscopic examination. 



Outline of Experiments 



I, May 4. Owing, probably, to too great dilution of sperm and 

 too great a length of time between removal from the body and the 

 attempt at fertilization of the ova, neither the irradiated or the 

 exposed sperm fertilized any ova. 



II, May 5. Sperm exposed for two hours to X-rays about four 

 inches from the tube. A large number of the spermatozoa were 

 active at the end of this period After fertilization the control and 



