( 7# ) 
tliefe Hboks out of' Fig. 5, I was convincedg that that 
which i took for a Hook, was only a fecond Cafij ot 
Sheath for the other two, as you may fee by Fig. 5, 1. K. 
wherein likewife the Hollownefs does plainly appear. 
Now as we have prov*d the fecorid Cafe to be hollow, 
there is alfo a Cavity to be feen in Fig. 4. Of which we 
were confidering whether it might not contain a (harp 
Liquor, that we commonly call Poyfon> 
From ihis Difcovery,/tis eafy to conceive that fuch 
Flies don^t only lay their Eggs on the Leaves of Trees, 
but that they doaUb make an opening in the Skin et 
the Leaf, and convey an Egg intoit,irom whence comes 
the Worm, which gnawing the Veffels for its fuftenance, 
occafions the Sap to flow out of them, and to coagulate 
into that knotty fubftance. 
Moreover, one little Fly , produced one of thofe 
fmal! Worms, whofe^ hinder part was 9lfo hooked, much 
like that fort ot Flies that come from the Lice olr Wofms 
on Currant Trees. 
I took out two Tonnekens from tho betore-mention'd 
knobs in Willow Leaves, that were no bigger than Corns 
of courfe Sand, that I might defcribe the fhape of fuch 
a fmall Creature, but three hours after I miffed thern, 
and concluded, that in that time 'they were turned to 
Flies, and got away. • ^ - 
I have taken dead Worms out of the (aid knobs, 
v/ithout being able to find the leffer fort of Worm that 
ufes to devour the other, but L oblerved two longifli 
white things upon the dead Worm, which were fo very 
fmall, that they efcaped my nake^d Eye 5 I fancy 'd that 
they were Eggs, for I could fee nothing of them that 
was like a Worm^ and the third day there plainly ap- 
peared two Worms exadly of the fame fize and fliape of 
thofe little Worms which I have faid do devour the 
greater. 
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