File:Discovery (20773712978).jpg

Title: Discovery
Identifier: discovery0304londuoft (find matches)
Year: [1] (s)
Authors:
Subjects: Science
Publisher: London (etc. ) Professional and Industrial Pub. Co. (etc. )
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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Fig. 2.âGYNANDROMORPHS OR SEX-MOSAICS. (a) Pine moth (Bupalus pinaritis); female on left, male on right. â (6) Ant (MyrmicH scahrinodts) ; male on left, worker (sterile female) on right. Reproduced from " The DeterminaUon of Sex," by Prof. L. Doncaster, F.R.S., â by permission of the Editors of the "Journal of Genetics" and of the Cambridge University Press, different sex-linked factors, sex-linked characters also could be different in the two regions of the body. In mammals, these sex-mosaics, as we may call them, do not occur, because the substances secreted bv the reproductive org-ans pass into the circulation, and influence the sexual characters equally all over the body. .â ^n even more remarkable abnormality is provided by what are called intersexes. The gipsy moth, that terrible forest plague, has a well-marked varietv in Japan. When this is crossed with the European race, verv curious results are obtained. When a Japanese male is crossed with a European female, 50 per cent, of the offspring are normal males, but the remainder are intermediate between male and femaleâso-called intersexes. \\'hen these are carefully examined, it is seen (by an examination of their hard parts, -which, once formed, cannot be remoulded) that thev have started their development as females, but ended it as males. They are females which suddenly, during their growth, have by some invisible but inexorable power been switched over to become of the opposite sex. .All degrees of inter.sexuality are known, according to the races employed in the cross. The females may show only the faintest traces of maleness; may be equally male and female; may be preponderatingly male ; or finally, in certain crosses, the change of sex may come so early that no trace of female characters appears, and the cross results in males alone. (.See Fig-- 3-) Even though half of these all-male broods ought by rights to be females, yet all behave like normal males, and can mate and produce offspring. \\'ith these experiments, carried out over a long series of vears by Professor Goldschmidt, of Berlin, we can at last be sure that it is possible for a complete and func- tional reversal of sex to take place. When the cross is made the other wa\-, with a Japanese female and a European male, the first generation is altogether normal. But in the second generation abnormal individuals again appear. This time, however, they are different from those first seen, and on analysis turn out to be intersexual malesâi.e., animals which have started as males and been forced to finish their development as females. What is the explanation of these strange facts? It appears to lie, ultimately, in the different climates to which the different races are adapted. The Japanese races are adapted to grow more rapidlv.
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Fig. 3.âGIPSV moth (Lvmantria dispar) ; SERIES OF INTERSEXU.^L FEMALES. .\bove. slight intersexuality; below, almost complete transformation to maleness. Br permission of the Editor of the "Journal of the Royal Society of Arts.'* (.ifter Goldschmidt.) The factor which produces maleness must lie in the sex (X) chromosome, which in moths is double in males, single in females. The factor producing femaleness we cannot yet locate so definitely; but it has been shown to be transmitted always and only through the mother; let us call it Q. Then all the

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