[ ] 
If one only propolis to one's fdf, to examine for 
fome moments the figures and the mot ons of 
water-infeds, one may content ones felf bare y with 
expofing fuch in the common way to the micro- 
fcope in a few drops of water. But 1 da e fpely 
allure, from divers repeated experiments, that it will 
often happen, tyith regard to feveral forts of thefe 
mfeds ? that the fimple obfervation of them in a 
drop or two of water, will not be fufficient to dif- 
cover all that is Angular either in their fhape or 
motion. It is therefore very proper than an ob- 
ferver Ihould endeavour to examine fuch infeds, 
when they are more at eafe, and in a larger quan- 
tity of water. And this he will find Bill more ne- 
ceffary, if he is deftrous regularly to purfue their 
hiftory. For then the fame infeds ought to be re- 
gularly obferved, for many days fueceffively, and 
they ought themfelves alio to be as nearly as poffi- 
ble under the fame circumftances they would have 
been, had they remained in the fame waters, ip 
which they naturally live. 
1 have accuftomed myfelf to keep great numbers 
of the fmall infeds I make obfervations upon, in 
large glaffes : and it is by obferving what paffes in 
thofe glaffes that I endeavour to difcover the more 
general fads, relating to the natural hiftory of thefe 
animals. After which, I have found by many re- 
peated experiments, that it is neceffary to remove 
into glaffes of a leffer fize, like that reprefented in • 
Fig . i. fuch of the infeds as are to be fet apart for 
more particular and curious microfpical obfervations* 
I put water into thefe glaffes, from the fame ditches, 
out of which the infeds I am obferving have them- 
felves 
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