230 Biology in America 



been performed on insects, frogs, birds and mammals. Better 

 nutrition is supposed to produce more females and vice versa. 

 In this way the attempt has been made to explain the increase 

 in males in France during the Napoleonic wars. One observer 

 has cited data showing that among the nobility of Sweden 

 the proportion of males to females is 98-100, while among the 

 clergy the ratio is 108.6-100. Another has shown on the 

 contrary that in London the more well-to-do have a larger 

 percentage of sons than daughters. Temperature, age of 

 parents and ripeness of eggs are other popular factors in 

 sex determination. But one of the most naive of recent 

 theories supposes that there is a regular alternation of male 



A HUMAN "MONSTER " 

 Courtesy of Dr. Oeo. L. Streeter. 



and female producing ova in man, the former coming from 

 the right, and the latter from the left ovary, and that sex 

 might be determined by the position of the prospective mother, 

 whether lying on her right or left side. 



Extensive experiments have been conducted on the influ- 

 ence of external factors in determining the sex cycle in par- 

 thenogenetic animals. The most familiar example of this type' 

 is the bee, in which the unfertilized egg gives rise to a male 

 (drone) and the fertilized to a female (queen) or an unde- 

 veloped female (worker). Here sex depends upon the act of 

 fertilization, and is probably determined by the chromosomes, 

 which differ in number in the two sexes. The influence of 

 food in controlling development is here most beautifully 



