Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2024-12-26T13:11:20.069Z Has data issue: false hasContentIssue false
  • English
  • Français

II.—Prenatal Death in the Pig and its Effect upon the Sex-Ratio

Published online by Cambridge University Press:  15 September 2014

F. A. E. Crew
Get access

Extract

The cytological evidence concerning the pig is that the sex of the future individual is determined at the time of fertilisation, and that in respect of the elements of the sex-chromosome sex-determining mechanism the male is digametic. If this is so, if the two sorts of sperm are produced in equal numbers, if each kind is equally viable and functional, and if fertilisation is at random, then a primary sex-ratio (that which obtains at the time of conception) of equality must follow. If male and female zygotes are equally viable, then the secondary sex-ratio (that which obtains at the time of gestation) will also be equality. A secondary sex-ratio other than equality must be the reflection of an unequal primary sex-ratio, the result of a differential production of the two sorts of gametes elaborated by the digametic sex, of a selective fertilisation by these, or of a sexually selective mortality among the embryos or/and fœtuses. A secondary sex-ratio of equality can follow a pronounced inequality in the primary sex-ratio if a sexually selective mortality operates prenatally.

Type
Proceedings
Information
Proceedings of the Royal Society of Edinburgh , Volume 46 , 1927 , pp. 9 - 14
Copyright
Copyright © Royal Society of Edinburgh 1927

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

LITERATURE

Corner, C. G., 1921, “The Internal Migration of the Ovum,” John Hopkins Bull., 32, 77–83.Google Scholar
Corner, C. G., 1923, “The Problem of Embryonic Pathology of Mammals, with Observations on Intra-uterine Mortality in the Pig,” Amer. Journ. Anat., 31, 523–545.CrossRefGoogle Scholar
Hammond, J., 1921, “Further Observations on the Factors controlling Fertility and Fœtal Atrophy,” Journ. Agri. Sci., 11, 337–366.CrossRefGoogle Scholar
Machens, , 1915, “ Fruchtbarkeit und Geschlechtsverhältniss beim veredelten Landschwein,” Berl. Tierärztl. Woch., 31, 559–562.Google Scholar
Parker, and Bullard, , 1913, “On the Size of Litters and the Number of Mammæ in Swine,” Proc. Amer. Acad. Arts and Sci., 49, 399–426.CrossRefGoogle Scholar
Parkes, A. S., 1923, “ Frequencies of Sex-combinations in Pig Litters,” Biometr., 15, 373–381.CrossRefGoogle Scholar
Parkes, A. S., 1925, “The Fœtal Sex-ratio in Pigs,” Journ. Agri. Sci., 15, 284–299.CrossRefGoogle Scholar