« lxvui ) 
specialisation in the matter of variety of food; and, in the 
next place, the function of nutrition shows a most important 
difference in insects and in Vertebrata. Immediate per- 
fection of tissue-assimilation is the point of importance in the 
nutrition of Vertebrata, and for this régime varié is, on the 
whole, probably favourable. But in insects in the larva- 
stage, tissue-assimilation is subordinate in importance to the 
accumulation of unformed tissue for the purposes of a fnture 
stage: is it not probable that ‘‘meat from a single dish’”’ 
may be favourable to this curious and imperfect form of 
assimilation ? Ifso, M. Fabre’s argument, instead of shaking 
the theory of common descent, actually helps to support it. 
But whether this be the case or not, it is at least certain that the 
hypothesis on which M. Fabre bases his argument is a very 
doubtful one, for there may be, —indeed, I think there are,— 
other reasons for supposing that meat from a single dish 
may be more advantageous to the insect larva than régime 
varié. 
I must now briefly apologise to you for the imperfect 
manner in which I have treated the great subject I have been 
discussing. Insect-instinct, indeed, is one of the most difficult 
problems that the biology of the future will have to deal with, 
and it must be very long before we can pronounce any very 
positive opinion as to whether it is favourable or unfavourable 
to the theory of evolution. To many it no doubt may seem 
unsatisfactory that we should have discussions on discussions 
and never come to a positive conclusion on any important 
point. Nevertheless, the subject is undoubtedly somewhat 
advanced by such means, and the fact that a long time must 
elapse before a clear comprehension can be attained is no 
sufficient reason for abandoning the attempt to comprehend. 
The value of such societies as ours consists, indeed, partly in 
the fact that they facilitate the extension of discussion beyond 
the period of a single life, and their existence is to some 
extent a guarantee that any efforts we may make towards 
the elucidation of difficult subjects will not be thrown away. 
It now only remains for me to thank you, gentlemen, for 
the unvarying consideration you have exercised towards me 
during the period of my presidency, and most cordially to 
