鳥類雜種の不妊性に關する研究

II. 鳩の種間雜種に於ける生殖器系の組織學的研究

抄録

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).