Descriptions of enhanced crossing over in the second chromosome of Drosophila ananassae are given here, as a continuation of the writer's previous papers (Moriwaki 1937a, 1937b). 1. The locus of Minute-In (M-IIb), which was believed to be situated near the left end of the second chromosome and also to be related with the enhancing power of crossing over, was, on the contrary, found to be in the right arm. 2. Concerning the relation between M-IIb and the enhancing power, it is concluded that this power cannot possibly be derived from M-IIb itself, but that it must be independent, and further, that the enhancer may be regarded as a dominant gene, Enhancer-II (En-II), probably belonging to the right arm similar to M-IIb. 3. It must be true that the enhancer ought to be able not only to increase somewhat the female crossing over, but also to induce male crossing over. 4. While it is remarkable that, except M-IIb and En-II, all the mutants (about 20) found in the second chromosome belong to the left arm, we cannot, judging from the figures of the salivary gland cells, say that the right arm is almost inactive. The interpretation that the mutability of genes in that arm is quite low, is preferable.
According to the genetico-physiological studies of the production of flower-colours in Pharbitis Nil, the coexistence of four complementary genes Ca, C, R, A is essential for the production of anthocyanin pigments in flowers. Among these genes, two genes Ca, C concern with the production of flavones from which anthocyanin is derived, gene R takes part in the function of converting flavones into anthocyanin, with the cooperation of gene A. The formation of the colour in the stem is developed by the coexistence of three genes Ca, R, A the gene C being non-related with them. The gene A which is considered as activators of the gene R, is composed of two duplicate genes, so far as the studies have covered. However, the present studies indicate the fact that the gene A is composed of five genes denoted as A1, A2, A3, A4 and A5, and also that three, perhaps five among these genes are duplicate ones. The function of the gene R is made active by anyone of these polymeries. In the presence of the gene Ca, every gene of these recessive genes or a1, a2, a3, a4 and a5 results in a white flower with green stem, as well as the recessive r of the gene R. Thus the white flower with green stem in this plant is numerous in genotype, though the flower-tube is either coloured or white. Each hybrid from two crosses worked out between two white flower strain which are same in appearance, in other words same phenotype, segregates four phenotypes as its offspring, but does not always give them in the same ratio of the segregation. Crossing a green stemmed white flowered strain which has a coloured flower tube, its genotype being CaCRa, with a coloured stemmed white one, its genotype being CacRa, the hybrid results in a coloured flower which is entirely unlike to both parents. And the offspring of the hybrid gives rise to four phenotypes i. e., coloured flowers, green stemmed white ones with the coloured flower-tube, colored stemmed white ones with white flower-tube, and green stemmed white one with white flower-tube, in the normal dihybrid ratio. On the other hand, the hybrid from a cross between a green stemmed white flower strain with coloured flower-tube of the genotype CaCrA and a coloured stemmed white one of the genotype CacRA, bears equally coloured flowers, as well as the hybrid from the cross mentioned above, while though the offspring contain four phenotypes, they do not segregate four phenotypes in the normal dihybrid ratio, but give such a segregation that shows the occurrence of a linkage. The linkage happens between c and r, the recombination value being the variation from 25.0±1.40% to 38.9±3.01%. Then, two genes c and r are inserted into the Yellow linkage group. The linkage group into which five genes a1, a2, a3, a4 and a5 are inserted, is as follows : gene a1 which may be identical to Dr. Imai's w2a is inserted into the Duplicate linkage group, gene a2 into the Contracted one, together with gene a3 which may be identical to his w2b, gene a4 into the Variegated one, gene a5 into the Cordate one.
The authors (1937a) reported that (1) the intensity of nature of winter growth habit in wheat varies with varieties, a variety without this nature being an absolute spring variety ; (2) this “winter nature” is cancelled completely or partially either by a low temperature during germination and early growth or by a short-day condition under which young plants grow ; and that (3) in a case where a cancellation of winter nature is insufficient on account of high temperatures or long days, earing is retarded and becomes late or ceased owing to residual winter nature. They (1937b) reported also that, in a greenhouse culture (ca. 22°C), F1 hybrids of all the crosses SE (varieties with lower winter or higher spring nature, earlier earing) × WL (varieties with higher winter nature, later earing) were later in earing than the respective SE parents but earlier than WL, while those of all the crosses SL × WE were earlier than either of the respective parents. This phenomenon was interpreted as follows : The low winter nature is dominant or nearly so over the high, and in the earliness apart from the retarding influence of winter nature the F1 behaves its earing between both parents. Then, F1 of SE × WL can not be earlier than SE but is of course earlier than WL. In SL × WE, earing of WE is retarded by the residual winter nature owing to the high-temperature condition and is not early in this case in spite of its early genetic factors ; whereas F1 has spring or low winter nature as SL parent and its earing is influenced by the early genetic factors coming from WE parent, and becomes earlier than either of SL or WE. Spring sowings carried out at various dates with a WL × SE cross and 4 WE × SL crosses showed similar results as in the greenhouse culture mentioned above. In each WE × SL cross, the number of days earlier in F1 as compared with WE parent was increased with lateness of sowing. This is due to the retardation in WE parent by the increased residual winter nature and to the fastening in F1, owing to higher temperatures and longer days towards the later season. When germinated seeds were chilled at 1°C for 80 to 100 days before sowing and winter nature was thus cancelled, F1 became between both parents in earing as expected in all sowings even in WE × SL. In genetic experiments on earliness of wheat, the result may be, provided more or less degrees of winter nature is concerned, quite unlike according to the different degrees of cancellating action of winter nature, due to the difference of locality, sowing time, yearly climate, etc.
In the previous paper (Ômura, 1939) it was reported that, so far as the Spermato-prostatic reaction is concerned, there occurs no remarkable difference in the behavior of the spermatozoa nor, as well, in the nature of the prostatic secretion, between Bombyx mori and Lymantria dispar. That fact inspired the present study, the main object of which is to learn the fate of Lymantrian spermatozoa artificially inseminated into the bursa copulatrix of the female moth of Bombyx, in hope of making some contribution to the problems on the isolation of species and to the knowledge of specific difference of spermatozoa. First, as a control experiment, Bombycian spermatozoa taken from the vesiculae seminales and ampullae ductuum deferentium of virgin male moths were activated by adding their own prostatic secretion, and then they were inseminated artificially into the bursae copulatrices of female Bombycian moths (cf. Omura, 1936). All of the experimented females successfully received the semen in their bursae copulatrices and laid many fertilized eggs. In their receptacula seminium, as to be expected, there were found abundant spermatozoa (Table 1). Next, the Bombycian spermatozoa gathered as above and activated by Lymantrian prostatic secretion were injected artificially into Bombycian bursae copulatrices (Table 2). Three of five experimented females were fertilized, while the remaining two proved to be unfertilized. After examination, however, it was found that these unfertilized females also had received the semen in their bursae copulatrices and one of them had a small amount of spermatozoa in its receptaculum seminis. The poorer rate of success in this experiment than in the former seems to be due simply to the difficulty of operation caused by the delicacy of Lymantrian prostata, which is very small in size, being only some one-tenth that of Bombyx. The evidence herein obtained is sufficient to show that the prostatic secretion of Lymantria can give a quite normal activity to the spermatozoa of Bombyx. Since it was known from the author's previous study (Ômura, 1938) that the spermatozoa of Bombyx become fertile only when they are activated by mixing with prostatic secretion of its own, the results from the above two experiments seem to indicate that, so far as the function of activation of spermatozoa is concerned, the prostatic secretion of Lymantria is very near to, or the same as, that of Bombyx, and its function is not specific to its own spermatozoa. Third, Lymantrian spermatozoa taken from the virgin male moths as in the case of Bombyx, and activated by adding with prostatic secretion either of Bombyx or of Lymantria were injected artificially into bursa copulatrix of Bombyx. In this case they never reached the receptaculum seminis, and, of course, never entered into the egg cells of Bombyx (Tables 3 and 4). However, it has been left for future study whether the Lymantrian spermatozoa make some progression in the Bombycian female genital organs, from the bursa copulatrix toward the receptaculum seminis. Anyhow, on the basis of the present study, it may be concluded that between Bombyx and Lymantria the difference in physiological character of spermatozoa in respect to time movement, is so decisive that Lymantrian spermatozoa cannot arrive at the egg cells in the Bombycian female sexual system, even if they are rid of those ecological and mechanical conditions which, in natural state, prevent the first step of their invasion into the Bombycian female genital organs. From the physiological aspect of spermatozoa of the Lepidoptera it is still considered from this investigation that the spermato-prostatic reaction does not represent any essential physiological function of spermatozoa.