( 259 ) 



On the fourteenth of Auguft, I faw four fully formed Flies flying 

 about the glafs, and that the fhells or velicles from which they had 

 ifTued, had a hole at one end : upon my putting fome fugar under 

 the glafs, the Flies immediately fed iipon it. 



The next day all the other aurelias or grubs produced living Flies 

 except two which I had injured in the handling, and at the fame 

 time I perceived many other Flies on the glafs in my clofet, which 

 T concluded came from the maggots which had hid themfelves as 

 before mentioned. I placed before thofe Flies fome pieces of raw 

 flefli, but none of them would feed on it ; neverthelefs, on the 

 eighteenth of Augull:, they all fed greedily on a piece of flelli. 



On the twenty-eighth of Auguft, I opened three of thefe Flies, 

 and took out of one of them a great quantity of oblong eggs, each of 

 which was a twenty-fifth part larger than the eggs I had taken out 

 of the Flies which were not hatched ; and what appeared to me 

 worthy of note was, that to each of thefe eggs was fixed an ex- 

 ceeding fmall black vefl'el, through which I conclude each egg had 

 received its nourilhment. All thefe minute velTels arofe out of 

 larger and darker coloured velfels, and thofe again out of a much 

 larger one ; all which veflels I therefore concluded to be arteries. 

 Examining thefe arteries with great attention, I very diftin(3;ly per- 

 ceived them to be formed of annular parts, like the veflels in the 

 lungs of animals, but thefe annular parts were fo exceedingly mi- 

 nute, that, viewed through microfcopes of very great magnifying 

 powers, they appeared as slender as a fine hair of one's head iccn 

 by the naked eye. 



Though thefe Flies appeared very vigorous, yet a fmall touch or 

 prefliire would caufe them to die ; for happening to break one of 

 the glafles in which I kept them, whereby they efcaped, and flew 

 about my ftudy, though in catching them I handled them as gently 

 as I was able, they died in a few days ; fome lofmg their wings, by 

 which I had caught them, others the ufe of their legs, and laying 

 on their backs motionlefs for feveral days,; and I concluded their 



Kk2 



