( cxxx ) 



foz'mer, and can only develop in proportion as the former 

 become feeble and defective." * 



The bearing of Insect Warnhig a7id Mimetic Colours upon the 

 supposed hereditary transmission of exj)erience by their Verte- 

 brate enemies. — Adaptations which facilitate the education of 

 entomophagous vertebrates are so perfect and so vride-spread 

 in insects that they constitute a large body of indirect evidence 

 in favour of the non-transmission by heredity of the results of 

 experience. Fritz Muller, in his celebrated theory of mimicry, 

 suggested that the object of the likeness between the warning 

 colours of specially-protected species was to reduce the danger 

 from the attacks of young and inexperienced enemies. This 

 is all the more interesting because, as Professor Meldola has 

 pointed out, " in 1879 the question of the non-transmission of 

 acquired characters had not been brought into prominence. 

 It was tacitly assumed in the theory of Bates that a know- 

 ledge of edible and inedible types could be transmitted by 

 heredity. It is remarkable that Miiller, by virtue of his 

 hypothesis, should have unconsciously challenged this tacit 

 assumption by suggesting that young birds had to learn by 

 experience, and did not derive their knowledge of eatable and 

 distasteful forms by heredity. The whole tendency of Prof. 

 Lloyd Morgan's work of late years has been to confirm the 

 suggestion by actual observation and experiment ; and Mr. 

 Finn, also, in summing up this result, states that ' each bird 

 has to separately acquire its experience, and well remembers 

 what it has learned.' Thus the Miillerian theoi-y of 1879 has 

 now been placed on a psychological basis of well-ascertained 

 facts." t 



The problem has been attacked from both sides with 

 concordant results. In contemplating the vast scale upon 

 which these aids to memory and education are developed, it is 

 necessary to take into account the pressure of the struggle for 

 existence upon the enemies themselves. " This pressure is 

 chiefly felt by the young, and it is so excessive that compara- 

 tively few individuals in the fresh wave sent forth at each breed- 

 ing season, survive to become mature and experienced. It 



* From the Jubilee Volume of the Soc. de Biol, of Paris, 1899, 

 Reprinted in "Nature," vol. Ixi, 1900, pp. 624—625. 

 t " Nature," vol. Ix, 1899, p. 57. 



