_ 
( exxmiv. ) 
irrelevant and tedious, whatever did not seem to bear upon 
the main thesis, namely, that the God of Nature has furnished a 
certain insect with the essential archetype of an unimprovable 
Tenon Saw. 
I feel sure that if any one whose ideas of a Sawfly and its 
operations are derived from any modern text-book will take 
the trouble to see what Réaumur really had to say on the 
subject, he will be simply amazed to find how much more 
intelligible and convincing the story is in its original shape, 
and will feel as I do, what a pity it is that Réaumur’s 
work, which was once in the hands of every entomologist in 
Europe, should have become what is called a Classic—that is 
to say, a book which every one has heard of and no one 
reads ! 
I will now indicate briefly a few reasons which convince me 
that the Sawfly’s implement, as a whole, cannot properly be 
called a saw, ideal or otherwise. By saying as a whole, I 
mean to save myself from denying that certain small parts of 
it may act in a sense as saws. Consider what we mean by 
sawing as opposed to other methods of dividing solid sub- 
stances. <A toothed edge (the teeth nearly always “set ”’—i. e. 
deflected alternately to right and left) is applied more or less 
horizontally to some such material as a piece of wood, and 
this the ‘‘ teeth” scratch, tearing away and pushing before 
them small fragments (sawdust), and gradually forming a 
groove of increasing depth, but constant width (this being 
determined by that of the “ set”), into which a considerable 
portion of the blade slowly and evenly descends. Such a 
descent would obviously be impossible if the thickness of the 
saw, at any part of it which was to enter the groove, should 
exceed the width of that groove, or (which comes to the same 
thing) the space included between the tips of the teeth. If the 
teeth were not deflected at all, the blade would have to be 
thinner still—practically an object of only two dimensions, 
length and breadth. Next, the blade being already partly 
embedded, the teeth have to go on scratching, and in whatever 
direction they move the blade must, of course, move too. If it 
cannot do so, the saw is said to “jam,” and the work cannot 
proceed. Accordingly, not only must the blade be limited as 
