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XXII. Obfervations on the Aphides of Lin- 
naeus, by Dr, William Richardfon, of 
Ripon, Yorkfhire : Communicated by 
William Heberden, M. D» F,R, S, 
Read Mar. 14, he learned Limcetis "by his un- 
wearied application having reduced 
the various produdions of nature into one regular 
fyftem, and clearly diftinguidied the numerous tribe of 
infeds into their diftind clafTes and fubdivihons, feems 
to me to have laid a more folid foundation for the 
natural hiflory of thefe minute animals, than any 
other writer who has gone before him. Difficult, 
however, as it is to lay fo firm a foundation, the 
fuperftrudure muff dill be efteemed a more ar- 
duous undertaking j as it is eafier to diffinguifh the 
outward form, even of the minutefl infeds, than 
to difcover their internal nature and difpofition. 
This is a knowledge not to be attained by any fingle 
perfon, be his genius and diligence ever fo great ; 
but to bring it to any degree of perfedion, will re- 
quire the joint endeavours of the curious in all ages, 
and in all the different parts of the world. From 
which confiderations, I am induced to throw in my 
mite towards promoting fo ufeful an undertaking ; 
by reducing my obfervations on this furprizing kind 
of infed, into a more concife and regular form. 
4 Though 
