40 Charles Russell Bardeen 



There is a slight increase over the normal amount of connective 

 tissue in the body. The pigment cells are abnormally scattered 

 about. 



Musculature — The muscles are fairly well differentiated in the 

 head. The more anterior of the myotomes are fairly normal but 

 in the posterior half of the embryo they are not well developed. 



Skin — In many places the skin shows abnormal outgrowths 

 especially about an irregular opening into the body cavity. 



SUMMARY AND CONCLUSIONS 



Toad spermatozoa removed from the body begin to lose both 

 motility and fertility within half an hour. Both motility and 

 fertility last much longer on cool than on warm days and some- 

 what longer in unexposed than on spermatozoa exposed to the 

 Roentgen rays. On cool days the power of fertilizing lasts in some 

 of the spermatozoa over two hours. When only ten or fifteen per 

 cent of the control eggs are fertilized as a rule few or none of the 

 eggs placed with the exposed sperm are fertilized. 



When only a few eggs are fertilized by the exposed sperm as a 

 rule these eggs do not develop beyond the gastrula stage, but 

 occasionally one may develop into an abnormal tadpole. 



When the spermatozoa have been well exposed to the rays and 

 yet are still capable of fertilizing a considerable number of eggs, 

 the eggs thus fertilized develop at first apparently normally or 

 even better than the control, but beyond the gastrula stage the 

 development begins to become retarded and at the time of hatch- 

 ing, as the tail begins to grow out, marked deformities appear in 

 the larvae. These deformities are visible externally and are still 

 more striking when the internal structure is examined. The 

 illustrations given on Plates II to V illustrate these deformities 

 more readily than they can be described in words. While they 

 vary considerably there are certain features characteristic of most 

 of the tadpoles. 



General Development 



Growth of the tadpole is inhibited beyond the stage which in- 

 tervenes between hatching and the time when it should begin to 



