( clxxviii ) 



dry-season forms with intermediates of Precis octavia octavia, 

 Cram., and Precis octavia sesamus, Trimen, from West and 

 South Africa respectively, for comparison. He also remarked 

 on a series from the Nuba Hills, Soudan, exhibited by Prof. 

 Poulton, and pointed out that, contrary to the Tembora 

 series, the dry-season forms were all pure dry-season, no inter- 

 mediates being present. The wet-season form appears also 

 to be paler. • 



Dr. G. A. K. Marshall said that he had bred many inter- 

 mediates under abnormal conditions, and that any kind of 

 shock seemed efficacious in bringing about this result. 



Lord Rothschild said that in experiments on Aglais 

 urticae he had found that it was only during a very short 

 period just before hardening that the pupa was susceptible 

 to surrounding influences. 



Paper. 



The following paper was read : — 



" Butterfly Vision," by H. Eltringham, M.A., D.Sc, F.Z.S. 

 The paper was illustrated by means of lantern slides showing 

 the structure and optical action of the butterfly eye, and the 

 author also described and illustrated a series of experiments 

 designed to test the capacity of butterflies for perceiving 

 colours. He had arrived at the conclusion that the optical 

 image provided for the perception of the insect's brain was 

 at least eight times more distinct than had been supposed 

 under previous theories, and also that though the butterflies 

 with which he had experimented were in some cases rather 

 " short " at the red end of the spectrum, there was strong 

 evidence that they could distinguish at least those colours 

 with which they were associated in life. 



Dr. Longstafp warmly complimented the author on his 

 paper and recalled one of his own observations in Jamaica 

 where a yellow butterfly had selected and settled upon a yellow 

 leaf lying on a wide area of uniform green. Dr. Eltringham 

 had mentioned a very remarkable fact in connection with the 

 actinic properties of the yellow flowers of the Rudbechia, and 

 he had himself observed the overwhelmingly brilliant effect of 



