( Ixvi ) 



i'or, iiniess tlie two eyea could be eiffiultaneously fticuased 

 on the same object the estimation of distance, which deter- 

 mined the idea of size, could only take place by the knowledge 

 of the effort made to secure the focus of one eye, instead of 

 by the system of unconscious trigonometrical survey, which 

 was one of the main sources of the knowledge of distance 

 employed by frontal-eyed animals; unless, indeed, it were 

 considered that the angle was measured iirst with one then 

 with the other eye by quick movement of the head. 



With monocular vision, where the distance was not exactly 

 known, a small object nearer the beholder might svibtend a 

 greater angle than a larger similar one further off, and, if 

 unfamiliar, be mistaken for the greater. 



The idea of distance was one of the more slowly-acquired 

 concepts ; but the eyes of the yovmg of all animals were quickly 

 taken by conspicuous pattern. 



Coloration, at one extreme, served to break up the apparent 

 mass and protectively obscure it, while at the other it invited 

 attention as some glaring label ; a Poison label, which would 

 denote danger to the consumer of the contents of the object 

 bearing it, and, as in the case of the Poison label, the danger 

 would exist irrespective of the size of the "label" and the 

 object it protected. Perhaps it might not be too strong an 

 assumption to consider that the young inexperienced enemy, 

 tasting the gaudily-coloured, distasteful Acnea, would be 

 impressed, more by the coloration — by the Poison label — 

 than by the size of the object, and afterwards would avoid 

 similarly-coloured objects which crossed its field of vision, 

 without taking any conscious account of their size. 



Paper. 

 Mr. Edward Saunders, F.R.S., contributed "A Supple- 

 mentary Note to a Paper entitled ' Hymenoptera Aculeata 

 collected by the Rev, A. E. Eaton, M.A., in Madeira and 

 Tenerife, in the Spring of 1902.'" 



Wednesday, December 2nd, 1903. 

 Professor Edward B. Poulton, M.A., D.Sc, F.Pt.S., Pre- 

 sident, in the Chair. 



