X-RAYS AND REPRODUCTIVE ORGANS OF RAT 333 



We are not certain if the metabolic changes in the irradiated host, or 

 true mutations in the germ cells, are responsible for the defective progeny. 

 The data obtained for the F^ are not sufficient to give an answer. 



Following the Fg we found that the percentage of dwarfs and the mortality- 

 rate was not reduced. Moreover, in the Fg generation we observed in some 

 cases anophthalmia and microphthalmia which was not recorded in Fj 

 (Table IV). Our breeding experiments are still in progress. Out of 405 rats 

 belonging to Fg, 268 have reached the age when their defectiveness could be 

 seen. They are the progeny of 13 exposed females. It seems that the damage 

 to the germ cells is not of the same type in all irradiated rats. Only one 

 exposed female out of 13 had progeny without a case of dwarfism or mortality 

 in Fj and F2 generations. Five of them showed a decreased percentage of 

 defectiveness in Fg, compared with F^. Five exposed females gave defective 

 progeny only in the Fg generation. Two irradiated females produced some 

 defective rats in Fg which were different from aU others. One of these two has 

 11 rats in F^ and 40 animals in Fg with no case of dwarfism, but we found 3 

 animals in Fo with anophthahnia and microphthalmia. The other exposed 

 female has, in the Fg generation, 2 female dwarfs with heavy anaemia 

 accompanied by the anisocytosis of red blood corpuscules. The circulatory 

 blood of all other normal and dwarf rats was examined and no similar case 

 was found. On the basis of the incomplete data obtained for the F2 we are 

 inclined to believe that serious genetic damages to the germ cells had been 

 produced by exposure to the dose of 50 r. We hope that a foUow-up of the 

 F3 and F4 will help us solve the problem. 



ACKNOWLEDGMENT 



The authors want to express their gratitude to Prof. Z. M. Bacq for 

 encouraging them in their work. 



EEFERENCES 



Mandl, a. M. (1959). Proc. roy. Soc. B150, 53. 



Mandl, a. M., and Zuckerman, S. (1951). J. Endocrinol. 7, 112. 



Peters, H. (1961). Radiation Res. 15, 582. 



EussELL, L. B., and Russell, W. L. (1956). In "Progress in Radiobiology" (J. S. 



Mitchell, B. E. Holmes, and C. L. Smith, eds.) p. 187. Ohver and Boyd, London. 

 RussEL, W. L., RussEL, L. B., Steele, M. H., and Phipps, E. L. (1959). Science 129, 



1288. 

 Spalding, G. F., Wellnitz, J. M., and Schweitzer, W. H. (1957). Fert. and Steril, 8, 80. 



