REPRODUCTION OF POLYPES AND APHIDES. 283 



that if the body of the Hyclra " be merely irritated with a 

 needle, or a ray of the sun, a young one will sprout from 

 the injured parts."* Here Harvey's dictum receives direct 

 contradiction : the Polyjie which is produced from a wound 

 in the body of the parent, being in every respect similar to 

 the Polype which is produced from an egg. 



It was in ] 744 that Trembley made known to the world 

 the astonishing reproductive powers of the Hydra. -f- The 

 following year I Bonnet published his not less astonishing 

 revelations on the reproduction of Aphides, or plant-lice. 

 The Aphis, a winged insect familiar to most readers, 

 deposits its eggs in the axils of the leaves of plants at the 

 close of summer, and these eggs are hatched in the follow- 

 ing spring ; but the insect which issues from the egg is a 

 wingless sexless insect. It was known that this wingless 

 insect brought forth its young alive. Bonnet proved that 

 this took place when no male insect was present — in fact, he 

 proved that the insect was a virgin mother, and astoundingly 

 fertile. He isolated the young Aphis as soon as it was 

 hatched, reared it in strict seclusion, and watched it daily, 

 almost hourly, with the patient tenacity of a naturalist of 

 genius. He has left on record his anxieties, his tremulous 

 agitation lest its death should supervene to frustrate his 



* Reports of the Penzance Natural History Society, 1850, p. 571. Schleiden 

 says of the Oesneria, that a puncture in the leaf produces a bud, in a few days. 

 The two cases are precisely similar. 



t Trembley : Memoires sur un genre de Polypes dJeau douce, 4to, Leyden, 

 1744, 



X Bonnet : Traiti d^Insertologie, 2 vols., 1745 ; vol. i., p. 26, et seq, A 

 better edition is that printed at Amsterdam, 1780. 



