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136 THE BALANCE OF NATURE. 



Clover always produces most seed in the iieigh- 

 borliood oi" towns, where cats are abundant. And 

 the reason is siin[)ly this. The clover-blossom has 

 a very long tube, concealing its honey ; and the 

 honey can be reached by only one insect, the 

 liumble-bee, which has a proboscis long enough 

 for tlie purpose. Hence only humble-bees ferti- 

 lize the clover, carrying the pollen from one blos- 

 som to another on their hairy legs. Accordingly, 

 the more bees, the more clover-seed in any par- 

 ticular meadow. But humble-bees themselves are 

 largely kept down in nuud)er by field-mice and 

 harvest-mice, wliich feed upon tlieui ami thin 

 their nests with great voracity. Here we get 

 another link in the chain — tlie more field-mice, 

 the fewer humble-bees, and therefore in the end 

 the less clover-seed. Once more, cats eat rats 

 and mice, and among the fields in the neighbor- 

 hood of towns harvest-mice are far less numerous 

 than elsewhere, owing to tlie depredations of their 

 feline enemies. The more cats, tlie fewer field- 

 mice, the more humble-bees, and so finally the 

 more clover-seed ! Professor Huxley has even 

 pushed the chain of causation in this case one 

 link farther back, and ventured to add that the 

 setting of the clover-pods was ultimately influ- 

 enced by the nuud)er of old maids in the adjacent 

 towns ; for are not old maids in the last resort the 

 great cat-keepers? Thus we might almost say, if 



