CORRESPONDENCE OF RAY. 401 



Mr. Rat to Mr. Derham. 



Sir, — I find tbat you have been very curious in ob- 

 serving the generation of gnats, to which I must needs 

 own myself to be a great stranger, having never seen any 

 aurehae of that insect but those with club-heads, whence 

 I suppose om- most common gnats come. Of the ver- 

 miculi or nymphge, previous to these aurelise, T knew 

 nothing ; and now I perceive that the change of one of 

 these into the other is not instantaneous, by the casting 

 of a skin, as the change of the am-elia into a gnat, but 

 gradual, so that this seems to be a different sort of genera- 

 tion from the rest of this kind. 



I think you need not doubt but that the perfect gnat 

 lays the eggs in all these kinds, and that those that are 

 fecund are rendered so by the coition of the male and 

 female ; for this is agreeable to the process of nature in 

 the generation of all insects, none ever generating till 

 they have run through all their changes. As for the 

 suddenness of laying their eggs after their leaving the 

 aurelia state, that need not startle you, for it is usual for 

 many of them to couple and lay eggs so soon as ever 

 they are come out ; the females also may drop their eggs 

 without any coit, if there be no male near. 



From these different sorts of vermiculi and aurelise 

 doubtless do proceed various kinds of gnats, notwith- 

 standing I find but two described in authors. Howbeit 

 I think you mistake in charging Swammerdam with that 

 error, for I find in my French copy of him these words : 

 " Car nous en trouvons des plusiem's sortes." You will 

 deserve well of those who apply themselves to the history 

 of insects, if you shall find out, describe, and distinguish 

 these species. 



For my own part, I am now almost threescore and fif- 

 teen years of age, so that it is time for me to give over 

 these studies and inquiries ; and besides, I am so lame, 

 and almost continually afflicted with pain, that I cannot 



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