VOL. v.] PHILOSOPHICAL TRANSACTIONS. 497 



being exhausted, they continued restless, moving all of them in the top of the 

 water, and though some of them seemed to endeavour to go to the bottom, 

 and dived some part of the way, especially with their heads, yet they were im- 

 mediately buoyed up again. Within an hour or a little more they were all 

 motionless, and lay floating on the water; wherefore I opened the receiver, 

 upon which the air rushed in, and almost all of them presently sunk to the bot- 

 tom, but none of them recovered. 



Exp. II. — We afterwards included a lesser number of tadpoles in a smaller 

 glass, which was also exhausted with the like circumstances with the former. 

 And when I found the other tadpoles dead, I hasted to these, which did not, 

 except perhaps one, give any sign of life ; but upon letting in the air, these 

 having not been long kept from it, some few of them recovered, and swam up 

 and down lively enough for some time; though after a while they also died. 



Exp. III. — Some years after I repeated the same experiment in a portable re- 

 ceiver of a convenient kind; and though after the exhaustion was perfected, the 

 tadpoles did for a while move briskly enough on the top of the water (none of 

 them appearing able to dive or swim under water) yet coming to look on them 

 at the end of an hour, they seemed to be all of them quite dead, yet continued 

 floating. And though within half an hour after that, I let in the air upon 

 them, yet all the effect of it was, that the most of them immediately sunk to 

 the bottom, as the rest did a very little while after; none of them, that I could 

 observe, recovering any vital motion. 



Exp. IV. — ^We procured with much difficulty some of those odd insects 

 which I elsewhere describe, whereof gnats have by some ingenious men been 

 observed to be generated about the end of August, or beginning of September. 

 These for some weeks live all together in the water (as tadpoles do) swimming 

 up and down therein till they are ripe for a transmigration into flies : which it- 

 self is so great a rarity in nature, as makes these little creatures recompense to 

 our curiosity the trouble they often give our faces and hands. Supposing then 

 that, if I could get some of these, and include them, being of those insects 

 they call aquatilia, and so minute as they are, they may live a great while in the 

 receiver without air, and in the mean while attain the period, which, according 

 to nature's course, is wont to turn them into flies, which might come forth 

 winged creatures into a medium not furnished with common air, as others of 

 their kind enjoy ; supposing, I say, that these insects would affbrd me some in- 

 formation about these particulars, having upon much watching met wuth four or 

 five of them after a shower of rain, that dropped from a house into a vessel laid 

 on purpose for it, we included them with some of their water into a small glass 

 receiver, which being very exactly closed, we kept in a south window, where 



VOL. I. 3 R 



