and a heightened percentage of boys; with the recurrence of prosperity and an increased number of marriages and births, the percentage of female births rises (though it never equals numerically that of the males).[7] More children are born from warm-weather than from cold-weather conceptions,[8] but relatively more boys are born from cold-weather conceptions.  Professor Axel Key has shown from statistics of 18,000 Swedish school children that from the end of November and the beginning of December until the end of March or the middle of April, growth in children is feeble.  From July-August to November-December their daily increase in weight is three times as great as during the winter months.[9] This is evidence in confirmation of a connection between maleness, slow growth, and either poor nutrition or cold weather, or both.  Professor Key’s investigations[10] have also confirmed the well-known fact that maturity is reached earlier in girls than in boys and have shown that in respect of growth the ill-nourished girls follow the law of growth of the boys.  Growth is a function of nutrition, and puberty is a sign that somatic growth is so far finished that the organism produces a surplus of nutrition to be used in reproduction.  Organically reproduction is also a function of nutrition, and, as Spencer pointed out, is to be regarded as discontinuous growth.  The fact than an anabolic surplus, preparatory to the katabolic process of reproduction, is stored at an earlier period in the female than in the male, and that this period is retarded in the ill-nourished female, is a confirmation of the view that femaleness is an expression of the tendency to store nutriment, and explains also the infantile somatic characters of woman.  Finally, the fact that polyandry is found almost exclusively in poor countries, coupled with the fact that ethnologists uniformly report a scarcity of women in those countries, permits us to attribute polyandry to a scarcity of women and scarcity of women to poor food conditions.

This evidence should be considered in connection with the experiments of Yung on tadpoles, of Siebold on wasps, and of Klebs on the modification of male and female organs in plants: 

According to Yung, tadpoles pass through an hermaphroditic stage, in common, according to other authorities, with most animals....  When the tadpoles were left to themselves, the females were rather in the majority.  In three lots the proportion of females to males was:  54-46, 61-39, 56-44.  The average number of females was thus about fifty-seven in the hundred.  In the first brood, by feeding one set with beef, Yung raised the percentage of females from 54 to 78:  in the second, with fish, the percentage rose from 61 to 81; while in the third set, when the especially nutritious flesh of frogs was supplied, the percentage rose from 56 to 92.  That is to say, in the last case the result of high feeding was that there were 92 females and 8 males.[11]