Studies on sex-determination in amphibians. IV. The effects of external factors, acting before or during the time of fertilization, on the sex ratio of Bufo lentiginosus / Helen Dean King.

  • King, Helen Dean, 1869-1955.
Date:
1910
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Licence: In copyright

Credit: Studies on sex-determination in amphibians. IV. The effects of external factors, acting before or during the time of fertilization, on the sex ratio of Bufo lentiginosus / Helen Dean King. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    IV. The Effects of External Factors, Acting Before or During the Time of Fertilization, on the Sex Ratio of Bufo lentiginosus. HELEN DEAN KING, The Wistar Institute. At the present time practically all of the investigators who are working on the problem of sex-determination believe that the sex of a zygote is fixed at a very early period, and that it is not dependent upon environmental factors acting during embryonic development. There is considerable diversity of opinion, however, regarding the time when sexual differentiation takes place and the way in which it is brought about. A number of investigators, among whom may be mentioned Rauber (’00), Beard (’02), Schultze (’03) and Russo (’09) main- tain that sex is determined in the ovary, chiefly by nutritive conditions. According to this view mature eggs are either male or female, and the spermatozoan can take no part whatever in determining the sex of the egg it fertilizes. Other investigators, prominent among whom are Stevens (’05), Wilson (’06) and Morgan (’07, ’09, To), are inclined to the opinion that sex is not determined until the time of fertilization, and that it is the spermatozoan that definitely and unalterably fixes the sex of the individual. These two views are apparently irreconcilable, and such an array of seemingly indisputable facts has been brought forward in support of each of them that it may.be, as Jordan (’09) has recently suggested, that “sex has been attained by several paths, and is now determined in different modes and at different times in the different groups of animals and plants.” If this be true, it will be futile to try to find a single factor, or set of factors, that is the fundamental cause of sex in all organisms; and in- vestigations in this field must be confined to an attempt to dis-