( 36 ) 
former, and can only develop in proportion as the former 
become feeble and defective.” * 
The bearing of Insect Warning and Mimetic Colours upon the 
supposed hereditary transmission of experience by their Verte- 
brate enemies,—Adaptations which facilitate the education of 
entomophagous vertebrates are so perfect and so wide-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 Miiller, in bis 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 theory of 1879 has 
now been placed on a psychological basis of well-ascertained 
facts.” 7 
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. lxi, 1900, pp. 624—625. 
+ ‘‘ Nature,” vol. lx, 1899, p. 57. 
