With a number of rice varieties and their F1 hybrids, the behavior of chromosomes in pollen mother cells was investigated. The occasional occurrence of univalent chromosomes, “stretched chromosomes”, and anaphasic bridges was pointed out. All of these abnormalities were found both in F1 plants and in parental pure lines, and in the frequency of occurrence of these phenomena, the F1 and parental plants did not differ significantly. Thus the anaphasic bridge cannot be attributed to inversion. An explanation may be that they come from an occasional reunion of sister chromatids after a breakage at the diplotene stage in meiosis.
The eggs laid by white-1 strain (female) mate with normal strain (male) are pale colored. This pale coloration is due to the fact that a part of kynurenine which exists in white-1 strain egg is changed into 3-hydroxykynurenine and then into the pigment by the function of +w1 gene of the male strain. However, there are cases in which white-1 strain is colored scarcely or deeply according to the different strains of the male used. An analysis of genetical causes of such different pigmentations proved that the genes which control the pigmentation are closely linked with white-1 gene. Moreover, after researching their positional relations with w2 and w3 located on 10th chromosome, this kind of genes were ascertained to be multiple alleles or pseudoalleles of w1 gene. From these results it has become evident that +w1 gene consists of a number of isoallelic genes having different expression in strength and that +w1 gene differs in a few strains.
In this paper, it is proved that the Curled wing (Cw), the Crayfish (cf) and Normal pupa are in the relation of multiple alleles. Consequently the symbol of the Curled wing (Cw) should be rewritten to cfCw from Cw. Apparent irregularities of segregation can be accounted for by the assumption that the penetrance of cfCw is rather low, while that of cf is almost complete.
In the former report (Toyofuku 1957) the author has dealt with twelve different kinds of salivary chromosomal aberrations found in Drosophila samples which were collected in 1955. Further investigations have revealed the occurrence of fourteen chromosomal aberrations in six species of Drosophila collected in 1956 from natural populations. Among them, nine types were found to occur in D. nigromaculata which were collected from five different localities, The remaining five types of aberrations were observed in the following five species: D. auraria, D. bifasciata, D. coracina, D. funebris and D. histrioides. The inversions occurring in D. immigrans and D. sordidula are of similar nature to those observed in 1955 by the author (Toyofuku 1957).