( V ) 



apex towards the base. Might it be inferred from this that 

 the insect's saw is made to cut not like the carpenter's saw by 

 a. push (outwards or forwards), but by a, pull (inwards or back- 

 wards), and if so, is it because the latter movement involves 

 less risk or damage to these delicate structures through bend- 

 ing or breakage] Again, what can be the use of certain 

 extremely fine denticulations (so small as to be only just 

 visible in the photographs) on the teeth themselves, not at 

 their apices, nor on that side of them which on the hypothesis 

 above would be their cutting edge, but at the base of each 

 tooth close to the sinus separating it from the tooth next 

 adjoining, so that it was difficult to see how their presence or 

 absence could assist the cutting action of the teeth 1 Might it 

 be that in some way they helped to clear the cut and prevent 

 clogging — the very "wide-set" of the teeth in most of the 

 saws shown suggesting that this had to be provided ' for — or 

 to make the saw less liable to " pinch," i. e. become jammed in 

 the cut, and remove any obstacle that might be met with in 

 withdrawing it when its work was done? Very little if any- 

 thing seemed to have been put on record, from actual observa- 

 tion of the process, as to the manner in which these saws were 

 actually employed ; and the exhibitor mentioned that although 

 he had long collected sawflies, both in England and abroad, he 

 had never been so fortunate as to see one actually at its 

 work. 



A discussion followed in which Prof. T. Hudson Beare 

 supported on the whole the hypotheses suggested by the 

 exhibitor. 



Dr. T. A. Chapman was strongly of opinion that the name 

 "saw" for these instruments, though well describing their 

 general appearance, was question-begging as regards their 

 function. They were really knives, all their cutting was done 

 during the forward movement, the notches being merely a 

 ratchet to hold one " saw " in place whilst the other advanced, 

 as they alternately moved. The " saw " must get in before it 

 could (if it did) saw, but if it can get in without sawing, it 

 can go on without doing so. The angle at which the margin 

 lies makes it certain that especially towards the point of the 

 instrument, the least retraction would free the saw without 



