THE DETERMINATION OF SEX. 



47 



SUMMARY. 



I. Nutrition is one of the most important factors in determining sex. In 

 illustration, note (a) the experiments of Yung, which raised the percentage of 

 females from 56 to 92 by good feeding ; (b) the case of bees, where the 

 differences between queen and worker well illustrate the enormous results of a 

 slight nutritive advantage ; also the case of humble-bees, with three successive 

 broods increasing in nutritive prosperity and in femaleness ; (c) Von Siebold's 

 experiments with a wasp, which showed most females in favorable conditions ; 

 (d) Aphides, in prosperity of summer, yield a succession of parthenogenetic 

 females, in cold and scarcity of autumn males return ; (e) starved caterpillars of 

 moths and butterflies become males ; (/) Rolph's observations on crustaceans ; 

 (g) also the facts noted by Girou, Diising and others, on the influence of good 

 nourishment of mammalian mothers in favoring female offspring ; (/;) the hints 

 of the same results in the human species ; (/) the various observations in regard 

 to plants which favor the same general conclusion. 



II. As to the influence of temperature, favorable conditions again tend to 

 femaleness of offspring, extremes to males. 



III. These factors are now added up, — (a) the nutrition, age, &c, of 

 parents ; (b) the condition of the sex-elements ; (r) the environment of 

 embryo. 



IV. The generalization is thus reached, — anabolic conditions favor 

 preponderance of females, katabolic conditions tend to produce males. 



V. But females have been already seen to be more anabolic, and males 

 more katabolic. This view of sex is therefore confirmed. 



VI. How does Weismann explain the determination of sex, which illustrates 

 an outside influence penetrating to the reproductive cells ? 



LITERATURE. 



See works mentioned in Chapter III., especially those of Diising, Geddes 

 (article "Sex," Ency. Brit.), Hensen, and Sutton ; also those of Eimer, Geddes, 

 and Rolph in Chapter II. 

 Dusing, C. — As before ; also, Die experimentelle Pruning der Theorie von der 



Regulirung des Geschlechtsverhaltnisses. Jen. Zeitschr. f. Naturwiss. 



XIV., Supplement, 1885. 

 Heyer, F. — Untersuchungen fiber das Verhaltniss des Geschlechtes bej 



einhausigen und zweihausigen Pflanzen, unter Berficksichtigung des 



Geschlechtsverhaltnisses bei den Thieren und den Menschen, Ber. 



landwirthschaftl. Inst. Halle. V. 1884, pp. 1-152. 

 Meehan, T. — Relation of Heat to the Sexes of Flowers. Proc. Acad. Nat. 



Science, Philadelphia (1884), pp. 111-117. 

 Semper, C. — The Natural Conditions of Existence as they Affect Animal Life. 



Internat. Science Series, London, 1881. 



