Notes on the proportion of the sexes in dogs / by Walter Heape.

  • Walter Heape
Date:
[1907]
Catalogue details

Licence: In copyright

Credit: Notes on the proportion of the sexes in dogs / by Walter Heape. 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.

    2/32 page 122
    moment at which the sex of the offspring can be determined is the time of fertilisation, and that no influence exerted sub- sequently can alter that sex. If these statements be true thei'efore, it follows that all this portion of the literature may be disregarded from the point of view from which it was written; at the same time it appears to me to be of considerable value from another point of view and well worthy of attention. The most recent writers on the subject claim that the sex of the generative products is governed by the laws of heredity, and, so far as I understand, the effect of extraneous influences on the sex of the progeny is wholly denied by them. I find reason myself to believe, that while each ovum and spermatozoan in the generative glands contains within itself sex, which is probably determined by the laws of heredity, that the proportion of those male and female ova and spermatozoa which are developed and set free from the generative glands may be regulated by selective action, exerted in accordance with the resultant of a variety of extraneous forces. If this be true the proportion of living male and female ova and spermatozoa which are freed from the generative glands, and the proportion of the sexes of the offspring which result therefrom, will thus be influenced. It is this aspect of the problem with which I specially deal in the following paper; and it is in this connection that I find the literature, referred to above, of interest. The very existence of sex demands that ova and spermatozoa or both should be themselves sexual, i.e. male, female, or hermaphrodite. Recent researches by Wilson (Journ. Exp. Zool. vol. 3, 1906) de- monstrate that the spermatozoa examined by him are histologically differentiated into two groups and it appears not improbable that these groups are male and female. If this be so, although histological evidence is wanting, there is no prima facie reason why ova should not be similarly differentiated, and the power some females possess to produce parthenogenetically in some cases functional males, in others functional females, points emphatically to that conclusion. In this relation the research of Doncaster “on the maturation of the unfertilised egg and the fate of the polar bodies in the Tenthredinidae” (Quart. Journ. of Mic. Sci, vol. 49,1906) regarding the product of conjugation of certain portions of the divided polar bodies in parthenogenetic eggs, is of great interest, and is strongly suggestive, to my mind, that the ovum, in all animals, is capable of determining the sex of the progeny. Apart from this latter point, to which I will refer below, it may I think be assumed that what is true for the spermatozoa
    digitised image 1
    digitised image 2
    digitised image 3