Sex determination.

Bacci, Guido.

Date:: [1965]

Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Sex determination. Source: Wellcome Collection.

62/328 (page 46)

46 SEX DETERMINATION is the opposite of sex differentiation—reduces inbreeding and favours heterosis. The study of processes involved with sexual reproduction actually shows many instances of different systems leading to quite similar results. It is difficult therefore to evaluate properly the actual role of certain biological processes in evolution and a cautious attitude must be recommended when dealing with general evolutionary problems. Critical viewpoints must also be given the utmost attention. Some authors contend (Canella, 1959) that the amphimixis theory and its recent enunciations totally lack experimental support and that some very successful groups of organisms reproduce without showing any trace of sexual processes. It must be pointed out, on the other hand, that sexual or parasexual phenomena are constantly being discovered in new organisms and that—in Weismann-Muller's theory—sexual reproduction is not said to be a necessity for the mutating plants and animals but only to confer great advantage to sexual over asexual organisms. It is also quite true that a number of panglossian speculations have been unduly advanced by a few followers of the amphimixis theory but it cannot be forgotten that its pragmatic value has received confirmation in the recent discoveries of sex processes in bacteria and viruses. Hartmann (1909, 1956) followed personal views and regarded sex as a basic property of the living matter which appears to be necessarily linked with fertilization: every organism, in Hartmann's interpretation, is endowed with a bipolar sexuality and with the potencies for male and female sex. This line of thought, which practically ignored the solution given by Weismann, stimulated a fruitful search for sex differentiation in organisms where purely morphological investigation had been unable to find any trace of sex polarity. The observation that copulation in protists, conjugation in Infusoria and gametogenesis in the few metazoa which usually reproduce through vegeta¬ tive processes, can be induced by a number of external agencies, gave rise to rejuvenation, hunger and metabolic theories of sex. Such theories, although they have been supplanted by the genetic theory of sex, should be recalled when the problem of how sex has arisen, will be ripe for experimental investigation.