SPONTANEOUS GENERATION 39 



gardens where nothing of the sort had been seen before. 

 Certain kinds of animals and plants are peculiar to parti- 

 cular countries ; what more likely than that they should 

 be the offspring of the soil? Fables and impostures 

 supported what all took to be facts of observation. 

 The great name of Aristotle was used to confirm the 

 belief that insects were bred from putrefaction ; eels 

 and the fishes called Aphyae from the mud of rivers. 

 A belief in a process of transmutation was often 

 combined with a theory of spontaneous generation. 

 Francis Bacon not only held that insects were born of 

 putrefying matter, but that oak boughs stuck in the earth 

 produced vines. 



Towards the end of the seventeenth century it 

 occurred to one inquiring mind that a particular case 

 of spontaneous generation, which had been accepted by 

 everybody without hesitation, was capable of a less 

 mysterious explanation. Francesco Redi (1626-1698), 

 physician to the Duke of Tuscany, published in 1668 

 an account of his experiments on the generation of 

 blow-flies. He found that the flesh of the same animal 

 might yield more than one kind of fly, while the same 

 fly might be hatched from diff'erent kinds of flesh. He 

 saw the flies laying their eggs in flesh, and dissected 

 eggs out of their ovaries. When he kept off the flies 

 by gauze the flesh produced no maggots, but eggs were 

 laid on the gauze. Redi concluded that flies are gener- 

 ated from eggs laid by the females. He also studied 

 insect-galls, and the worms which feed on growing 

 seeds. Like earlier observers, he was baffled by finding 

 live grubs in galls or nuts which were apparently intact, 

 and by the parasitic worms which are now and then 

 found in the brain-case and other closed cavities of 

 quadrupeds. Such instances led him to jump at the 



