74 DISCOVERY CH. 



experiment was proposed as one likely to lead to 

 interesting results. Bonnet was only twenty years of 

 age when he undertook this task. 



He filled a flower-pot with earth, and plunged it into a phial 

 of water, intended to supply the food-plant. A new-born aphis, 

 whose birth had been observed, was placed on the plant, and 

 all was covered up by a bell-jar, which was pressed into the 

 earth, so as to exclude other insects. An aphis found upon the 

 spindle-tree was selected for the first trial, which began on 

 May 20, 1740. Bonnet kept an exact diary of his observations, 

 which were made hourly or oftener during the day; a good 

 lens was continually employed. The aphis changed its skin 

 four times, and came to maturity on June 1, when the first 

 young one was born. By June 21, the unfertilised female 

 had produced 95 aphids, all born alive. Prof. L. C. Miall. 



A similar result was obtained the next year, when 

 two new-born aphids, isolated in the same way, produced 

 respectively 90 and 49 young. Five successive genera- 

 tions of aphids were then bred without the participation 

 of a male insect, and the result, which was contrary to 

 all that was then known of reproduction in nature, was 

 received with lively interest not unmixed with incredulity. 

 The life-history of these insects differs indeed from all 

 pre-conceived ideas. Bonnet's observations established 

 it to be as follows : both winged and wingless aphids pro- 

 duce young alive while food is plentiful, but as the winter 

 approaches this mode of reproduction ceases ; small 

 winged males then appear, and the females lay fertilised 

 eggs from which young aphids emerge in the following 

 spring. Aphids are thus born without the participation 

 of the male insect during mild weather, and their race 

 is carried on from one year to another by the eggs laid 

 by fertile females near the end of the season. 



The discovery of this intricate course of events is far 

 more wonderful than the achievement of any Arsene 



