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men who fet themfclves in oppofition to all new difcoveries, being 

 riveted to old opinions ; yet are themfelves too indolent to in- 

 vestigate the fubject, and the rather, as thefe refearches into 

 Nature's works are often very troublefome, and bring no gain or 

 profit. I ftiould endeavour to confute fuch opponents, did I not 

 think it would be loft labour ; and, indeed, I know not who 

 would bestow fo much labour as I have done on that minute and 

 despifed creature the Flea. 



During the fpace of two months and upwards, I put into the 

 hands of my maid-fervant four or more glafles, with cork ftoppers, 

 and directed her to confine in them as many as fhe could catch of 

 the largeft fort of Fleas, which are always females, with a caution 

 to handle them gently, that none of the veins or vellels in their 

 bodies might be injured ; and thefe Fleas I frequently removed into 

 frefh glafles, to preferve the eggs they laid from being foiled with 

 the excrements they voided, in which, by the way I have plainly 

 feen a great quantity of faline particles. Now, if, as has been 

 obferved above, in tvs'enty-four days a perfect Flea is produced from 

 an egg, we fee that in a fingle fummer, or rather from the month 

 of March to November, Fleas may be propagated feven or eight 

 times, and fo often may we be infefted by new generations of 

 them. 



Not content with the preceding obfervations, I at feveral times 

 trained up or nurfed the worms from the Fleas' eggs, till they grew 

 to their full fize, and I found that an egg in three days time pro- 

 duced a worm or maggot, and the worms or maggots in twelve or 

 thirteen days, or little more, came to their full fize. In particular, 

 about the middle of Auguft, I had two maggots, one of which 

 came out of its egg about two hours before the other : the firft of 

 thefe I glued to the point of a fmall brafs pin, and placing it before 

 the microfcope, I gave it into the limner's hand, directing him to 

 make a drawing of it, as nearly as he was able, for the worm 

 moved itfelf about violently. 



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