262 AN INTRODUCTION TO ZOOLOGY 



or vice versa; still others had male and female characters in 

 different parts of the same organ. The reproductive organs 

 were often partly male and partly female, and their character 

 could not be determined by the external appearance of the 

 gynandromorphs. Various explanations have been offered to 

 account for this peculiar condition, but as yet the data necessary 

 to decide the question have not been furnished. 



c. The Relations of Bees to Other Organisms 



Charles Darwin in " The Origin of Species " has used the bum- 

 blebee to illustrate " how plants and animals, remote in the scale 

 of nature, are bound together by a web of complex relations." 

 He found " that the visits of bees are necessary for the fertiliza- 

 tion of some kinds of clover; for instance, twenty heads of Dutch 

 clover (Trifolium repens) yielded 2290 seeds, but twenty other 

 heads, protected from bees, produced not one." ..." Humble- 

 bees alone visit red clover, as other bees cannot reach the nectar, 

 hence we may infer as highly probable, that, if the whole 

 genus of humblebees became extinct or very rare in England, the 

 heart'sease and red clover would become very rare, or wholly 

 disappear. The number of humblebees in any district depends 

 in a gieat measure upon the number of field mice, which destroy 

 their combs and nests. . . . Now the number of mice is largely 

 dependent, as every one knows, on the number of cats. . . . 

 Hence it is quite credible that the presence of a feline animal in 

 large numbers in a district might determine, through the inter- 

 vention first of mice and then of bees, the frequency of certain 

 flowers in that district!" (236, p. 65.) The influence of old 

 maids upon the number of cats was suggested by Huxley as an 

 addition to Darwin's illustration. 



Bees and Flowers. CROSS-POLLINATION. Bees in flying from 

 flower to flower gathering nectar and pollen accomplish what is 

 known as cross-pollination, i.e. the pollen from one flower is 

 carried by the bee to another flower. Cross-pollination seems to 

 be of advantage to the seed, since many flowers are structurally 



