22O A. RICHARDS AND DONNELL J. GOOD. 



The irradiation of Nereis eggs (Packard) before fertilization 

 frequently caused marked polyspermy, due to interference with 

 the jelly formation about the egg. In Nereis the amount of 

 jelly extruded from the egg at the time of fertilization is char- 

 acteristically large; a similar explanation here is doubtfully 

 possible in view of the smaller amount of jelly. 



There is also other evidence that fertilization is affected by 

 exposure to X-rays by means of a chemical change in the com- 

 bining substance in the egg or the sperm. Richards ('15) and 

 Packard ('16) have both shown the power of a short radiation in 

 effecting a chemical change in proteids and some enzymes. 

 Swartz ('08) found that exposure to radium is able to effect a 

 chemical change in lethicin. Hertwig ('14) showed the direct 

 effect of radiations of radium upon the chromatin content of the 

 cell. These instances all serve to render plausible the explanation 



here suggested. 



SUMMARY. 



1 . A short radiation of the fertilized egg of Cumingia stimulates 

 cell division for a time then retards it. A longer radiation pro- 

 duces less stimulation and a greater retardation. 



2. A short or long sperm radiation before fertilization if not 

 too intense affects the rate of cleavage in no way. 



3. A short radiation of the unfertilized egg causes, when 

 fertilized with normal sperm, a retardation in development, the 

 production of abnormalities and complete inhibition of growth 

 before the free-swimming larval stages are reached. 



4. A short irradiation of both sperm and egg before fertiliza- 

 tion results in a direct retarding of cleavage and in the pro- 

 duction of abnormal embryos, most of them never reaching the 

 free-swimming larval stage. 



5. Eggs fertilized by sperm that have been subjected to a 

 short exposure to X-rays result in a greater percentage of develop- 

 ing eggs than would normally occur. A long radiation produces 

 an indifferent result. 



6. An exposure to X-rays of the unfertilized egg results in a 

 lesser percentage of developing eggs upon fertilization by normal 

 sperm. No difference is evident due to time of exposure. 



7. Eggs and sperm each exposed to the X-ray before mixing 



