Scientific Proceedings. 



(243) 73 



cause not even the spermatozoa of the control dish proved capable 

 of fertilizing the eggs, owing to the time which had elapsed since 

 the removal of the sperm from the male, or because none of the 

 females happened to have ova in the right condition to be fertilized. 

 The thoroughly successful experiments, owing to the short season 

 of mating, were few in number but they were convincingly posi- 

 tive. All eggs fertilized by the control spermatozoa developed 

 normally. Only one egg in fifty to a hundred that were fertilized 

 by the exposed spermatozoa, developed at all normally. All the 

 others showed marked defects in development. 



The results of the experiments may be briefly summarized as 

 follows : 



1. The spermatozoa of the common toad retain power of 

 movement and fertilization for from one-half to nearly three hours 

 in a dish of lake water at room temperature. On hot days they 

 die sooner than on cool days. 



2. Spermatozoa when under exposure of Rontgen rays die 

 sooner than when not thus exposed. 



3. When spermatozoa are exposed to the rays so long that 

 very few are capable of fertilizing ova, the eggs thus fertilized 

 usually do not develop into larvas but they may do so. 



4. When spermatozoa have been exposed for a considerable 

 period to the Rontgen rays and yet are still capable of fertilizing 

 a considerable proportion of eggs placed in the same dish the 

 eggs seem to develop normally at first, but beyond the gastrula 

 stage the development becomes retarded and the resulting larvas 

 are markedly deformed. These deformities are quite varied. In 

 one larva for instance, a considerable part of the central nervous 

 system and the gills were undeveloped on one side while the 

 abdominal viscera were developed only on that side. In another 

 the central nervous system was abnormal on both sides and the 

 alimentary canal quite defective. Considerable further study is 

 necessary to determine accurately the nature of all the abnormali- 

 ties present in the various monsters the author has preserved. 

 Apparently all are defect abnormalities. 



From the results obtained it may be concluded : 



1. That nuclear material may be so influenced by exposure to 



the Rontgen rays that after a latent period it will call forth marked 



abnormalities in development. 



