EVOLUTION, HEREDITY, EUGENICS S33 



nourished ova produce females. Statistical studies negative this 

 hypothesis and indicate that the sexes are. about evenly distributed 

 regardless of the lunar cycle. 



Schenck suggested that the ripe eggs develop into males and the 

 unripe into females. He fed women nitrogenous food, induced 

 complete metabolism and males appeared, part of the time, of 

 course. In wasps and other insects it is well known that an abun- 

 dance of food induces greater numbers of females. In bees the 

 queen is procured by special " bee bread." H. D. King has shown 

 that neither food nor temperature is a factor in sex determination 

 in the frog. 



In Rotifers, D. D. Whitney and others have shown that a larger 

 number of male grandchildren are produced by feeding the female a 

 green unicellular organism, while if she is fed a colorless organism, 

 the offspring are practically all females. ShuU and Ladoff showed 

 that oxygen excess produced males but Whitney contended that 

 oxygen was not a factor. 



Robinson advanced the theory that the adrenals determine the 

 sex of the offspring, maintaining that an excess of adrenalin pro- 

 duces males, and that a smaller amount causes the development of 

 females. He based his conclusions on fifty clinical cases. Experi- 

 ments do not prove his theory, however. 



That there is an intimate relation between the genital glands and 

 the adrenals, the pituitary and the thyroids, cannot be denied. To 

 prove a specific physiological basis for the generally accepted action 

 of the chromosomes is a most difficult problem. 



The Accessory or Sex Determining Chromosome. ^^ — In 1891, 

 Henking found in the Hemipteran Pyrrhocoris a "peculiar chroma- 

 tin-element " which passes undivided to one pole while the other 

 eleven chromosomes are equally divided. He labeled it "X," and 

 finally termed it a "nucleolus." 



In 1901, McClung recognized the chromatin nucleolus of Henk- 

 ing as a chromosome which he traced (in the grasshopper Xiphidiu?n) 

 into the first spermatocyte, where it passed undivided to one pole, 

 then divided in the second spermatocyte, giving rise to two types of 

 spermatozoa. McClung was the first to suggest the bearing of two 

 kinds of spermatozoa on the determination of sex, and in 1902 he 

 called the sex chromosome the " accessory chromosome." 



15 Consult General Cytology, Chicago Press, 1924, and Wilson, E. B., The Cell, 

 1925, Macmillan and Co. 



