Archive image from page 199 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 184 CYTOLOGY CHAP. gigas. In the male meiosis of this hybrid, which has 21 chromosomes (14 + 7), according to Geerts (1911), we get 7 bivalents and 7 univalents ; of the triple set of chromosomes, two sets of homologues have paired, leaving the other set free, as is probably also the case in Drosera. Gates, however (1909 b), thinks it probable that there is no syndesis, and finds that there are 21 univalents in metaphase I. (in
Archive image from page 199 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar_0 Year: 1920 184 CYTOLOGY CHAP. gigas. In the male meiosis of this hybrid, which has 21 chromosomes (14 + 7), according to Geerts (1911), we get 7 bivalents and 7 univalents ; of the triple set of chromosomes, two sets of homologues have paired, leaving the other set free, as is probably also the case in Drosera. Gates, however (1909 b), thinks it probable that there is no syndesis, and finds that there are 21 univalents in metaphase I. (in the Oenotheras, the associa- Fig. 79. Side and polar views of the equatorial plate in the meiosis of certain Lepidoptera and their hybrids. (After Federley, , 1913.) A, B, Pygaera anachoreta, 30 bivalents; C, D, P. curtula, 29 bivalents ; E, F, P. anachoretaxP. curtula, hybrid; in E, 3 chromosomes are bivalent, the rest univalent; in F, 56 or 57 chromo- somes can be seen, two or three are bivalent, the rest univalent. G, H, secondary hybrid obtained by crossing the first hybrid back with P. anachoreta 9; in G a mixture of univalents and bivalents; in H, 56 chromosomes can be counted ; namely, about 30 large bivalents (the anachoreta chromosomes), and about 26 small univalents (the curtula chromosomes). tion between the constituents of the bivalents in the meiotic division is characteristically very loose). According to the latter authority these 21 chromosomes are separated at anaphase into groups of 10 and n, rarely 9 and 12. According to Geerts the constituents of the bivalents separate normally, sending 7 to each pole, while the remaining 7 uni- valents suffer various fates—some being irregularly distributed to the
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