The reproductive organs of hybrid brids which resulted from three species crosses in the fathily Colurnbidae (Aves) were subjected to thorough histological study.
(1) - Streptopelia-orientalis × Streptopelia decaocto (Figs. 1-6).
Five hybrid birds (F1) were obtained from the same cross, all of which were proved to be male from microscopical study of their gonads, and to have perfectly normal testes containing healthy germ cells in the process of normal spermatogeneis (see Figs. 2-6). One of these hybrids was back-crossed to Streptopelia orientalis _??_, and two fertilized eggs were obtained.
(2) Streptopelia chinensis × Streptopelia decaocto (Figs. 7-11).
Three F1-offspring, two males and one female, were obtained from this cross. They were fully ferfile and an F2-offspring (, Fig. 11) was yielded from their cross. Anatomical and histological examinations of their gonads indicate that the testes and the ovary as well, were quite normal and functional. In the seminiferous tubules of testes there were observed numerous germ cells in the regular course of maturation divisions (see Figs. 8-10).
(3) Geopelia cuneata × Geopelia striata (Figs. 12-23).
In this cross fourteen F1-hybrids were produced ; there were found both males and females in this fraternity. During their life time the male hybrids often performed sexual behaviour characteristic to the male sex, while the females showed no regular sexual behaviour and were completely sterile without laying even one egg. After being dissected out it was found that in the males testes were apparently normal and unexpectedly large in the regular position (Fig. 18), while no gonad-like body could be found in the female, a pair of rudimentary oviducts only being observable (Figs. 21-23). The testes seemed to be normal.in histological structure being made up of a number of well-developed seminiferous tubules (Fig. 19). Cytological observations revealed that the multiplication division of the spermatogonial cells proceeds in the regular manner, but the first maturation division becomes aberrant due probably to the failure of normal synapsis of the chromosomes (Figs. 12-13). As the result of this division there are produced abnormal secondary spermatocytes. Many of them undergo pycnotic, degeneration without metamorphosing into functional spermatozoa (Fig. 14), . Some of the spermatids seem to trans-form into deformed spermatozoa with irregular shape, but they all die without developing into ripe spermatozoa (Fig.s 15-16). The vas deferens of the hybrids were also abnormal in microscopical structure (Figs. 17 and 20).

View full abstract

Employingthe albino mouse, MUS musculus L., derived from the Carnegie Institution strain, as the material, the processes of maturation of the egg and the phenomena of fertilization were cytologically investigated.The first maturation division of the egg is completed prior to ovulation within the ovarian follicle. After the first polar body is extruded, the chromosomes remaining in the egg are immediatelydrawn into the equatorial plate forming the metaphase spindle of the second maturation division. In this condition the egg undergoes ovulation. Fertilization occurs in the upper portion of the oviduct. Shortly after insemination, the second division advances in its course and as a result the formation of the second polar body is brought about. Therefore, stages subsequent to the metaphase of the second division take place only after the entry of the spermatozoon into the egg. Insemination is a necessary antecedent to the second maturation division. After being completely formed into the spherical body, the female and male pronuclei are alike in appearance but distinguishable only by their size.
Detailed accounts on this subject will appear in the Journal of Science, Hokkaido Imperial University, Series VI, Zoology, Vol. 7, No. 4.

View full abstract

1) Observation has been made on the coloration of the compound eyes developed from implanted ocelli of the silkworm larva.
2) It has been ascertained that the colors of the eye and the egg are both determined by interaction of a hormone (W) and two chromogens (P, R) as follows :
WPR Black
WPr Red
WpR Pink wPR, WpR, wPr, wpr White
3) The intensity of color of the implanted eye differs by the sex of the host as the author reported previously. It is darker in the female host than in the male.
4) When more than two fragments develop in the same host, difference of coloration, if any, has no definite relation with the size of fragments, but perhaps depends upon the parts of the ocellus from which they had been derived.

View full abstract

(1) It is supposed that, in the male-intersexual plant used for this study, the chromosome fragments have no effect upon the sex-disturbance. The sex-disturbing-genes will be carried on certain autosomes, as in the ease of the other male-intersexual plants already studied by the author.
(2) In the somatic cells of the same individual in which the chromosome-fragments are involved, the number of chromosome-fragment is very variable. The cause of this phenomenon is explained in various ways.

View full abstract