226 Redi^s Expe7'iments on the Generation of Insects. 



he made many similar experiments, and always found that 

 uncovered meats shortly teemed with life ; while, on the con- 

 trary, those that had no communication with the external air, 

 corrupted, but never verminated. During the course of these 

 experiments, he ascertained the curious fact, that when the 

 common fly dies, it serves as a nest for its own species equally 

 with any other kind of dead flesh. Not yet satisfied, he deter- 

 mined on making a new experiment. He put some meat and 

 fish into a large vessel, covered with very fine gauze, which 

 he also put into a large box, covered with the same gauze, 

 that the air might penetrate to the meats, while it remained 

 free from the intrusion of insects. On these he did not see a 

 single worm, but frequently saw the little creatures writhing 

 about on the outer gauze, trying to make their way through; and 

 it was with difficulty that he was once quick enough to prevent 

 two of them from falling on the meat, for they had got their 

 bodies half through the inner gauze. He also observed the flies, 

 attracted by the meat, and unable to make their way to it, 

 drop their eggs upon the gauze ; some of them alighting upon 

 it, others hovering in the air during the operation ; and he 

 perceived that each left six or seven eggs at a time. This was 

 the point he wished to attain, and he had now discovered that 

 insects supposed to be engendered by corruption, were, in 

 reality, propagated by their own species. 



Notwithstanding his liberal philosophy, and his active ex- 

 perimenting, Redi falls into the most extraordinary error ; he 

 asserts that some plants, fruits, &c., produce insects. That one 

 who went so far should go no farther, but cease his experiments 

 just where he ought to have pursued them still more zealously, 

 appears incomprehensible ; it would seem that he had pur- 

 posely left to others the glory of finishing what he had so 

 nearly accomplished. It is the more marvellous, as in one 

 particular instance he was so near the truth. Let me use his 

 own words. Speaking of the galls in oaks, he says, " I freely 

 confess, that having made my first experiments on the gene- 

 ration of insects, I was inclined to believe, or rather suspect, 

 that perhaps the gall was caused by an insect, which, coming 

 in the spring, and making a little fissure in the tenderest 

 branches of oaks, secreted an egg in that fissure, which was 



the cause of the excrescence, and I was inclined to 



think that the gall was a disease, occasioned by the puncture 



of the fly, as we see tumours arise on the human body, 



from the same cause." After various doubts, he says, " It seems 

 more probable that the generation of insects born in trees, 

 should not be chance generations, nor caused by any fly de- 

 positing its egg there, as each gall has its particular insect^ a 



