VICTORY AND REST 161 



Cross and Self Fertilisation,' he proved by careful and 

 frequently repeated experiments that a constant in- 

 fusion of fresh blood (so to speak) is essential to the 

 production of the healthiest offspring. In the words 

 of his own emphatic summing up, ' Nature abhors per- 

 petual self-fertilisation.' 



The immediate result of these new statements and 

 this fresh rationale of Knight's law was to bring down 

 Sprengel forthwith from the top shelf, where he had 

 languished ingloriously for seventy years, and to set a 

 whole school of ardent botanical observers working hard 

 in the lines he had laid down upon the mutual corre- 

 lations of insects and flowers. A vast literature sprang 

 up at once upon this enchanting and long-neglected 

 subject, the most eminent workers in the rediscovered 

 field being Delpino in Italy, Hildebrand and Hermann. 

 Miiller in Germany, Axel in Sweden, Lubbock in 

 England, and Fritz Miiller in tropical South America. 

 Darwin found the question, in fact, almost taken out of 

 his hands before he had time himself to treat of it ; for 

 Hildebrand's chief work was published as early as 1867, 

 while Axel's appeared in 1869, both of them several 

 years earlier than Darwin's own final essay on the 

 subject in the Effects of Cross and Self Fertilisation.' 

 No statement, perhaps, could more clearly mark the 

 enormous impetus given to researches in this direction 

 than the fact that D'Arcy Thompson, in his appendix 

 to Miiller's splendid work on the ' Fertilisation of 

 Flowers,' has collected a list of no less than eight hun- 

 dred and fourteen separate works or important papers 

 bearing on that special department of botany, almost 

 all of them subsequent in date to the first publication 

 15 



