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SCIENCE 



[N. S. Vol. XXXIX. No. 997 



whole contents of horns were not compared, but 

 the pairs of animals next the right and the 

 left ovaries were contrasted, so far as their 

 sexes were concerned, with the pairs at the 

 junction of the horns, the presumption being 

 that the pure products of each ovary would 

 occur most frequently next that organ and the 

 mixed products of the two ovaries midway 

 between them. The details thus brought to- 

 gether are shown in the following table. 



TABLE 



This table shows the frequency of occurrence of 

 pairs of unborn pigs of various combinations of 

 sexes at the division of the horns of the uterus, 

 next the right ovary, and nest the left ovary. 



It is fair to assume that at the division of 

 the horns of the uterus the offspring are likely 

 to be as often from one ovary as from the 

 other. If in the whole population the males 

 and females are equally abundant, three 

 classes of pairs would be expected to occur and 

 in the following proportions: 25 per cent, of 

 the pairs would be composed of two males; 25 

 per cent, of two females ; and 50 per cent, each 

 of a male and a female. That this condition 

 is very nearly realized is seen from the table, 

 where it will be observed that the pairs of 

 males are present to the extent of 26.6 — per 

 cent., the females 25.3 + per cent, and the 

 pairs of the two sexes combined 48.1 + per 

 cent. The fact that the table shows a few more 

 pairs of males than females is due to the condi- 

 tion of the population as a whole, in which the 

 males outnumber the females by 1,026 to 1,000. 

 This slight digression from equality also has 

 its effect on the relation of the numbers of 

 pairs composed of both sexes to those of one 

 sex only, but the total number of records is 

 probably too small to yield very smooth results 

 in this respect. 



If, as Seligson maintained, the right ovary 

 gives rise to male and the left to female off- 

 spring, the pairs of pigs next the right ovary 

 ought to be predominantly males and those 

 next the left predominantly females. That 

 such is not the case is seen at once from the 

 table, where it is shown that pairs composed 

 of two males or of two females occur in about 

 the same proportions next the right ovary that 

 they do next the left, a proportion that is very 

 close to that occurring at the division of the 

 horns of the uterus. These statistics, there- 

 fore, give no support to hypotheses, such as 

 Seligson's, according to which the eggs from 

 the ovary of one side of the body produce off- 

 spring of one sex only. 



Although the sex of the offspring is thus 

 shown not to be correlated with the side of the 

 body from which the egg that gave rise to the 

 young came, it might be supposed that in any 

 female a given ovary would always produce 

 offspring of the same sex. In that case we 

 should expect to find the great majority of 

 pairs of young next the ovaries to be either 

 both males or both females. But, as the table 

 shows, there are almost as many pairs com- 

 posed of one male and one female next the 

 ovaries as there are at the division of the 

 horns. Hence we may conclude that in the pig 

 the ovaries by virtue of their position in one 

 or other half of the maternal body exert no 

 influence on the sex of the offspring, but that 

 each ovary produces eggs which may give rise 

 to either male or female offspring. This con- 

 clusion is in line with such experimental work 

 as that of Doncaster and Marshall (1910),* 

 and of King (1911)^ on albino rats, according 

 to which a single ovary, after the removal of 

 its mate, can give rise to eggs which produce 

 males and females. 



6. H. Parker 



January 23, 1914 



■* Doncaster, L., and F. H. A. Marshall, ' ' The 

 Effects of One-sided Ovariotomy on the Sex of the 

 Offspring, ' ' Jour. Genetics, Vol. 1, pp. 70-72, 1910. 



5 King, H. D., ' ' The Effects of Semi-spaying 

 and Semi-castration on the Sex Ratio of the Al- 

 bino Eat {Mus norvegicus albmus)," Jour. Exp. 

 Zool, Vol. 10, pp. 381-392, 1911. 



