250 C. P. SWANSON AND BeNGT KiHLMAN 



impression, however, that oxidative phosphorylation is 

 always involved in some of the steps in the chain of events 

 leading to chromosomal aberrations. The experimental data 

 so far available suggest that this step is toward the end of the 

 chain, and that it may be one normally occurring in the 

 chromosome. The metabolic events (stage IV) are probably 

 several in number, and the larger the number before the actual 

 induction of aberrations the less obvious will be the influence 

 of inhibitors of oxidative metabolism on chemical mutagenesis. 

 Admittedly we are treading on somewhat uncertain ground 

 in the above discussions. We have, for example, spoken of 

 breakage and rejoining as separable events in the induction of 

 chromosomal aberrations. This may or may not be so. At 

 the present time, the radiation experiments seem most 

 satisfactorily explained by making this distinction, but both 

 Revell (1953) and Loveless (1953), although differing in their 

 interpretations, agree in considering these two events insepar- 

 able so far as the induction of aberrations by chemicals is 

 concerned. The chemical experiments described above have 

 not yielded critical evidence on this point and further dis- 

 cussion of them will be reserved for subsequent papers where 

 a more detailed examination of the data can be made. 



REFERENCES 



Allen, A. O, (1954). Radiation Res., 1, 85. 



Allfrey, V. G., MiRSKY, A. E., and Osawa, S. (1955). Nature, Lond., 



176, 1042. 

 Beatty, a. v., Beatty, J. W., and Collins, C. (195G). Amer. J. Bot., 



43, 328. 

 Conger, A. D., and Fairchild, L. M. (1952). Proc. nat. Acad. Sci., 



Wash., 38, 289. 

 Deschner, E., and Sparrow, A. H. (1955). Genetics, 40, 460. 

 Ebert, M. (1955). Radiobiology Symposium (Liege), p. 30. New York: 



Academic Press. 

 Giles, N. H. (1954). Radiation Biology, Vol. 1, part 2, p. 713. New 



York: McGraw Hill. 

 Gray, L. H. (1953). Brit. J. Radiol., 26, 609. 

 Gray, L. H. (1954a). Radiation Res., 1, 189. 

 Gray, L. H. (1954fo). Acta Radiol, 4:1, 6S. 

 Kihlman, B. (1955). Hereditas, Lund, 41, 384. 

 KiHLMAN, B., and Levan, A. (1951). Hereditas, Lund, 37, 382. 



