Archive image from page 116 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 THE SEX CHROMOSOMES roT general use, X standing for the large sex chromosome and Y for the small one, the chromosome formulae of the two species is as follows {Lygaeus having like Proienor six pairs of ordinary chromosomes or ' Autosomes ') : Haploid. eggs all 6 + X. spermatozoa 6 + X or 6. eggs all 6 + X. spermatozoa 6 + X or 6 + Y. The cases are seen to be exactly parallel. There are two classes X Diploid. Protenor ? 12+XX 6 12 +
Archive image from page 116 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 THE SEX CHROMOSOMES roT general use, X standing for the large sex chromosome and Y for the small one, the chromosome formulae of the two species is as follows {Lygaeus having like Proienor six pairs of ordinary chromosomes or ' Autosomes ') : Haploid. eggs all 6 + X. spermatozoa 6 + X or 6. eggs all 6 + X. spermatozoa 6 + X or 6 + Y. The cases are seen to be exactly parallel. There are two classes X Diploid. Protenor ? 12+XX 6 12 + X Lygaeus ? 12 +XX 6 12 + XY »;• ; H Fig. 46 The chromosomes of Lygaeus turckus. (After Wilson, , 1905 and 1912.) A, spermatogonia telophase ; B, later telophase ; C, emergence of the massive chromatic bodies in the primary spermatocyte; D, leptotene stage; E, ' confused stage '; F, evolution of the bivaleuts; G, metaphase I.; H, I, daughter chromosome groups of anaphase I.; J, metaphase II., X and Y, now paired to form a bivalent; K, L, daughter chromosome groups from anaphase II. of spermatozoa in Lygaeus—one, the 6 +X form, will on fertiUzing an egg produce a female, the other (6+Y form) will produce a male. The process of meiosis in the male Lygaeus is illustrated in Fig. 46. This figure demonstrates the important fact that the sex chromosomes of the male often (though not in all cases; see below) remain compact throughout the whole meiotic prophase, including the leptotene and zygotene stages. It will be noted in Fig. 46, G, that X and Y are not paired to form
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