SEXUAL COLOKATION. 277 



the brilliaut colours of the male birds, for their appendages, 

 wattles, spurs and so forth, on the same grounds. 



It appears that among birds — and this is clearly the group 

 in which sexual selection must exist, if anywhere — the males 

 are more numerous than the females ; this at least is Mr. 

 Stolzmann's statement, based upon the examination of large 

 •series of birds collected by himself in Peru. A collection of 

 birds made by Mr. Guillemard during the cruise of the yacht 

 Marchesa in New Guinea and neighbouring islands contained 

 584 males, 285 females and 111 of undetermined sex; so that, 

 supposing the extreme case that all the 111 specimens were 

 females, there is still a preponderance of the opposite sex. 



Here is an obvious criticism upon the supposed fact, that 

 females are less numerous than males in collections of birds ; 

 the very fact that the females are shyer and harder to see, more 

 protectively coloured, often sitting upon the nest, renders them 

 less likely to fall victims to the gun of the collector ; hence, 

 possibly, the greater abundance of males in collections of skins. 



Another fact, upon which Stolzmann bases his ingenious 

 theory, is the influence of nutrition upon sex ; badly nourished 

 eggs produce males, well nourished eggs females. There are 

 other facts which tend to show that this is probably true. 

 The queen bee the only female in the hive, is produced from a 

 larva which has been specially "fed up" for that very purpose. 



Among insects there are other instances which tend to prove 

 the same generalisation— that excess of nourishment is favour- 

 able to the production of females, and that defective nutrition 

 is correlated with the development of males. Some interesting 

 experiments upon the subject were made some years ago by Mrs. 

 Mary Treat.* This lady found that larvte of a Swallow-tail, 

 Papilio aster ias, if encouraged to go on feeding as long as 

 * Aiuericaii yatandist for 1873. 



