The effects of X-rays on mitosis in the spermatogonial divisions of Locusta migratoria L

Although the fact that X-rays cause major structural alterations in chromosomes was actually known long before the discovery of their capacity for increasing gene mutation-rates our knowledge of the former type of effect has lagged behind. Nearly all the recent work on the biological effects of X-rays has been carried out on material such as vertebrate tissue-cultures which are extremely unfavourable for detailed study of chromosomes. Hence the very vague conceptions of the influence of radiation on the nucleus which are widespread in the literature; many authors referring to the sum total of these effects as the “sensitivity” of the nucleus to radiation. The literature dealing specifically with chromosomal abnormalities resulting from irradiation comprises only about nine papers (Helwig (1933); Huskins and Hunter (1935); Lewitsky and Araratian (1931); Mather and Stone (1934); Mather (1934); Navashin (1931); Stadler (1931); Stone (1933); and White (1935)). Of course, a great deal of work has been done on translocations and inversions produced by X-rays (e. g., Muller and Altenburg (1930): Muller, Prokofieva, and Raffel (1935)), but this only refers to cytologically and genetically viable abnormalities. It is obvious that these comprise only a small fraction of the total range of aberrations produced; the present paper, like those mentioned above, aims at recording all the artificially induced chromosome forms, whether capable of survival or not.