200 EIGHTEENTH CENTUR Y. PT. in. 



adding greatly to our knowledge of the structure of animals, 

 two famous naturalists in Switzerland and Italy were bringing 

 to light some extremely curious and interesting facts about 

 their growth. 



I The first of these, named gharlej^Bonnet, was born at 

 Geneva in ij 20, and died in i3. He had a great love of 

 /natural history, and when he was twenty years of age he 

 /wrote a paper upon aphides, or plant-lice, which was so re- 

 i markable that the French Academy of Sciences at once 

 jelected him one of their corresponding members. He 

 also made some very interesting experiments upon plants, 

 showing that they have the power of seeking out for them- 

 selves what is necessary for their growth. We all know that 

 plants grow towards the light, and if kept in a dark room 

 will seek out even a crack through which the light comes. 

 But Bonnet proved that they will do much more than this, 

 for he found that if he twisted the branch of a tree so as to 

 turn the leaves bottom upwards, in a little time each leaf 

 turned right round on its stalk so as to get back into its 

 natural position ; while on the other hand, if he hung a wet 

 sponge over a leaf, the leaf would turn its under side up- 

 wards, so as to bring the little mouths, or stomata, close to 

 the sponge, and enable them to drink in the water. In this 

 way a plant will always find out the best way of growing so 

 as to get as much sun and food as it can. Many curious 

 facts of this kind were published in Bonnet's work on the 

 ' Use of the Leaves of Plants,' but what I wish now particu- 

 larly to relate to you are his experiments upon animals and 

 the regrowth of limbs which had been cut off. 



It had long been known that very simple organisms, such 

 as polyps, may be cut in pieces, and each part will live and 

 become a perfect creature ; but no one thought it possible 

 that any of the more complicated living beings could be 



