1) In the male which is homozygous for the intersexual gene, no abnormalities appear in its sexuality, and accordingly such males occasionally used as sires.
2) As most of the sires were heterozygous for the intersexual gene in Japan, so the percentage of intersexes would be on the increase and will approach to 7.3% of occurrence in the near future. With the increase of intersexes, the homozygous recessive males also will be on the increase. If some homozygous, recessive males were used as sires in the herd, the occurrence of intersexual kids would become 14.6%, and if these were continued to mate in the herd, it would show the highest frequency of occurrence of intersexes, being attained to 25% of the total kids or 50% of the female ones.
3) To eliminate the intersexual gene, the proven sire must be used continuously for over seven generations, and when progeny test is difficult to apply, to use the horned male as the sire seems also to be the effective method of breeding.

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When the chromosomes in dividing cells were exposed to higher dosage of irradiation of X-ray, their matrixes showed various abnormal metamorphosis (Fig. 6 I, II, III and IV). It was shown that immediatly after the irradiation, direct proportional relation existed between the frequency of abnormal matrixes and the dose of X-ray (Table 1 and Fig. 5).
The frequency of various stage of abnormal matrixes were affected not only to the increase of the dose of X-ray, but also along with the passage of time after the treatment. Treated with the same dose of X-ray, the abnormality advanced with the passage of time after the irradiation (Table 1 and Fig. 6).

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This paper describes the outlines of both spermatogenesis and oogenesis observed in the pearl-oyster (Pteria martensii). The specimens for material were collected in Ago Bay, Mie Prefecture, during a period from the beginning of May to the beginning of June. The gonads were fixed with weak and strong Flemming's solutions and Lo Bianco's mixture. It was found that the ripening of both testes and ovaries took place at the same time in the individuals of the same age. The primary spermatocytes showed at metaphase 18 bivalents of small spherical shape. There were again 18 chromosomes in the secondary spermatocytes. In both the first and second divisions, the chromosomes separate into equal halves, showing no element characterized by a particular structure.
The occurrence of testis-ova was rather common in the testes, and the ovaries frequently showed the presence of many spermatozoa.

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That the voltinism of silkworms is under the genetic control is well demonstrated in the classical work of Watanabe (1918) who, having made analysis of the nature of the genes responsible for determination of the number of voltinism, observed that both the univoltine and the bivoltine are dominant to the tetravoltine, showing Mendelian ratio respectively. On the other hand, it is a matter of common observation that the voltinism is liable to be affected by changes of the environmental factors such as temperature and light. Also, in an earlier paper of the author (Umeya, 1925) it is pointed out, on the basis of the results of ovarian transplantation, that certain blood-born principe in the foster mother is significantly concerned with the determination of the voltinism.
Incidentally it was disclosed that the eggs of the original bivoltine strain always hatch out as univoltine under laboratory conditions unless they are subjected to the incubation at 15°C. Toward 1915, some of the Japanese bivoltine strains were distributed among egg-manufactures as the parents for hybridization. At that time the eggs of the strains always gave rise to bivoltine animals when they were incubated at 15°C. However, since the introduction of the methods of artificial hatching, such bivoltine races have been distributed for nearly 30 years without being subjected to the test by incubation at the low temperature.
Recently, an attempt was made in order to obtain non-wintering eggs from the bivoltine races widely distributed in Japan, to incubate the eggs at 15°C with an astonishing result that most of the eggs hatched out as univoltine. Taking into account various sorts of informations, the author has discussed the reason for such alternation. Two possible reasons have been conjectured, of which the one is interpreted on the assumption of unstable genes and the other is attributed to the artificial unconscious selection of bivoltine animals. Stress might be laid on the latter interpretation, but there is no concrete reason to reject the former possibility.
A word is added as to the problem of the origin of bivoltine character in silkworms, of which no determinative concept has been advocated. In view of the fact that bivoltine is recessive to univoltine, it appears most plausible that the character in question might have originated through mutation from the dominant univoltine character. On the basis of such an assumption, it may be inferred accorning to a rather classical saying that the reduction to univoltine of the Japanese bivoltine race through the prolonged influence of high-temperature incubation would represent an example of “reversion”.

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