Microscopical Essays. 



An aphis, or puceron, brought up in the moft perfect fblitude 

 from the very moment of it's birtli, in a few days will be found in 

 the midft of a numerous family ; repeat the experiment on one ofT 

 the individuals of this family, and you will find this fecond gene- 

 ration will multiply like it's parent, and this you may purfuer 

 through many generations., 



Mr. Bonnet; had repeated experiments of this kind, as far j& 

 the fixth generation, which all uniformly prefented the ©bferver 

 with fruitful virgins, when he was engaged in a feries of new and 

 tedious experiments, from a fufpicion imparted by Mr. Trembley 

 in a-letter to him, who thus expreffes himfelf : "I have formed! 

 " the defign of rearing feveraf generations of folitary pucerons, in 

 " order to fee if they would all equally bring forth young. In 

 " cafes fo remote from ufual cireumftances, it is allowed- to try alL 

 " forts of means ; and I argued with myfelf, who knows but that 

 "one copulation might ferve for feveral' generations ?" This, 

 "who knows" perfuaded Mr. Bonnet that he had= not 

 fufficiently purfued his inveftigations. He therefore now reared; 

 to. the tenth generation his folitary aphides, having the patience 

 to keep an exact account of the days and; hours of the birth of 

 each generation. He then difcovered both males and females, 

 among them, wfiofe amour* were not in the leaft equivocal;; the 

 males are produced only in the tenth generation, and are but few, 

 in number ; that thefe fo on arriving at their full growth, copulate 

 with the females, and that the virtue of this copulation ferves for 

 ten fucceiftve generations ; that all thefe generations, except the 

 flrft, from fecundated, eggs are produced viviparous, and all the- 

 individuals are females, except thofeof the 1 aft generation, among 

 whom feme males appear to lay the foundation of afrefh feries. 



