THE EFFECTS OF ONE-SIDED OVAEIOTOMY ON 

 THE SEX OF THE OFFSPEING. 



By L. DONCASTER, 



Fellow of King's College, Cambridge, 



AND F. H. A. MARSHALL, 



Fellow of Christ's College, Cambridge. 



{From the Physiology Laboratory, Cambridge.) 



It is now widely believed that sex is determined not by conditions 

 acting upon the organism after fertilisation, but by determinants or 

 " factors " existing in the gametes themselves. Since this view came 

 into prominence several hypotheses have been put forward, suggesting 

 that gametes bearing the factor for one or the other sex are produced in 

 separate gonads. Some have believed that in vertebrates one testis 

 yields male-producing spermatozoa, the other female-producing, but this 

 has been disproved in rats by Copeman^ It is also known to stock 

 breeders that bulls from which one testicle has been removed, give calves 

 of both sexes. Meanwhile evidence has been accumulated that in 

 several groups of animals it is the egg rather than the spermatozoon 

 which plays the more important part in sex-determination, and in 

 accordance with this, the opinion has been held that one ovary produces 

 female eggs, the other male eggs. That this is not a general rule is 

 proved by the case of birds, which have only one ovary, and in 

 Amphibia by the experiments of H. D. King^, but in a recent book^ 

 Dr Rumley Dawson has maintained that this hypothesis is valid at least 

 for man, and probably for other mammals. Direct evidence of a con- 



1 Experiments described at the Physiological Society, May 1908. 



2 Biol. Bulletin, xvi. p. 27, 1909. 



^ The Causation of Sex, London, 1909. 



