BONNET 285 



were published. Then came the important memoir by 

 Keaumur, published in the third volume of his Histoire 

 des Insectes (supra, p. 269). Leeuwenhoek and Cestone 

 had found no male aphids, and had got no proof that 

 the females were ever fertilised. Neither of them firmly- 

 established the fact, but they offered an explanation, 

 which was that aphids were self-fertilised — a daring 

 speculation, seeing that not a single case of a self- 

 fertilised animal could be quoted ! Cestone had thought 

 that the scale-insects too were self-fertilised, but Keaumur 

 was able to refute him by discovering the male insect. 

 Reaumur now thought of rendering the fertilisation of 

 an aphid by another individual impossible ; he meant to 

 isolate it from birth, and see whether it would still be 

 able to propagate. Owing to unlucky accidents, none 

 of the aphids which he thus isolated came to maturity, 

 but he did not lose sight of the inquiry, and when 

 Bonnet begged him to suggest a subject for investiga- 

 tion, Reaumur proposed this experiment as a promising 

 one. 



Bonnet came of a French Protestant family, which 

 had been driven by religious persecution to take refuge 

 in Switzerland. He was brought up to the law, but 

 found time for other studies, and among the rest for 

 natural history. Reaumur's Histoire des Insectes early 

 fixed his attention, and he was only twenty years old 

 when he undertook the aphis-experiment. The result 

 was communicated to Reaumur, and through him to the 

 Academic des Sciences, which begged him to repeat and 

 extend his researches. He did so, and followed up his 

 aphis-work by studying another case of abnormal repro- 

 duction, the multiplication of worms by section. A 

 weakness of the eyes hindered him from attempting 

 further work in natural history. Henceforth he gave 



