( jexzxyu } 
Others, no doubt, exist in libraries; but the above are all 
that I have come across. My knowledge of Italian is very 
limited, but with the help of a dictionary I have managed 
to work through the whole of his observations on what he 
calls the Mosca de’ Rosai, and to get a general idea of other 
treatises contained in the same volume, and more or less 
connected with it (though they cover a great variety of subjects, 
and are not entirely confined to Entomology). I gather an 
impression that the work was published with two main objects ; 
partly to confute views current in his day but now universally 
abandoned on the subject of Spontaneous Generation ; and 
partly to suggest a scheme of his own for a fresh classification 
of insects based entirely upon the differences of their life- 
histories. This notion, I must think, has proved to be some- 
what of an ignis fatwus ; for we all know now that similarities, 
whether of structure or habits, may be merely analogical and 
indicative of no real affinity; and yet I do not think that 
such a notion would have occurred at all at the beginning of 
the eighteenth century to a man who was not somewhat in 
advance of his contemporaries, and certainly @ priori it is not 
without considerable plausibility. However, returning to my 
present subject—the story of the Sawfly—I am bound to say 
that Vallisnieri’s treatment of it gives me a high idea of him, 
as a careful and thoughtful observer, an admirable describer, 
and a learned all-round naturalist and man of letters. Almost 
at the beginning of his account he makes a remark, which 
later writers (as far as I know) have not repeated, and which 
seems to me to be one of the most sensible and suggestive 
things that have yet been said on the subject—namely, that the 
process is analogous to that of ploughing ; it is furrowing of a 
suitable soil for the reception of seeds to be presently sown in 
it. This, to my mind, is both a truer and a more far-reaching 
simile than the more obvious one of the saw: it takes into 
account the ultimate objects of the whole operation ; it gives a 
truer notion of that which is most essential in the form and 
working of the organ—namely, that, whatever else it be, it is 
most certainly and obviously a wedge, and must inevitably act 
as such on every substance which it penetrates : 7. ¢. it proceeds 
mainly by pushing and, as it were, “ shouldering ” asunder the 
