380 PLANT PHYSIOLOGY 



a higher water content, and a higher metabolism than the second. 

 As the season advances and the birds get more food, all the eggs 

 have more stored food and the percentage of females increases. 

 Furthermore, female birds which come from eggs early in the 

 season often show secondary male characters which are lacking 

 completely in birds from eggs hatched later in the season. 



Goldschmidt (1916) has concluded from work on gypsy moths 

 that between the male and the female numerous sex-intergrades 

 occur and that the individuals of either sex may be made to 

 develop the characters of the opposite sex, the degree of change 

 depending upon the age at which the experiment is started. 



In Bonellia, a worm, the male is small and degenerate, living 

 parasitically upon the female. If the young are grown in an 

 aquarium by themselves, they develop into females, but, as Baltzer 

 (1914) has shown, if they are placed in with mature females, they 

 settle upon them and develop into males. By varying the time 

 they rest upon the female, all degrees of sex-intergrades may be 

 obtained. 



While in the human species, sex is connected with the chromo- 

 somes, the secondary sexual characters seem to be determined 

 by other factors, and various intergrades between the sexes are 

 not unknown. It is probable that even here masculinity and 

 femininity are relative terms with intergradations, so that the 

 100% male or female is of doubtful existence. In war and famine 

 the percentage of male children born is slightly higher than in 

 times of peace and plenty, which may be the result of a lack of 

 nutriment, thus connecting up the question of sex with nutrition ; 

 and Joyet-Lavergne has shown that the basal metabolism of males 

 is 6-7% higher than in females. The "suffragette" type is often 

 gaunt and slender; and the stage villain who traps the unwary 

 country maiden is never a fat man. 



In plants similar nutritional effects have been observed. If 

 dioecious fern prothallia are grown under poor nutrient condi- 

 tions, the relative number of antheridia is increased. Klebs, work- 

 ing with Vaucheria repens, which normally produces oogonia and 

 antheridia in equal numbers, found that when subjected to a 

 high temperature or reduced atmospheric pressure, the number of 

 oogonia was reduced and the number of antheridia increased, 

 with as many as five antheridia together and no oogonia. Similarly 

 Tiedjens (1928) showed that increasing the amount of sunlight 



