THE THEORY OF MIMICRY 153 



modifications of bodily .structure or habit which are im- 

 pressed on the organism in tlie course oi individual life/' 

 and hereditary " those characters and properties with 

 which the individual is originally endowed.'^ 



On page CXVIJI, referring to insect life and habits, 

 Prof. Poulton shows and affirms that heredity is alone 

 responsible. " The behaviour which leads to the produc- 

 tion of an elaborate cocoon or the burial of a larva in its 

 earthen cell is clearly instinctive, and the most convinc- 

 ing evidence Avould be required (evidence which it is 

 needless to say is entirely lacking) in order to prove that" 

 certain insects which perform an act no more elaborate 

 many times in their lives are guided by anything except 

 the compulsion of a '' nervous system built through here- 

 dity.'' 



" If the cocoon-making instinct has evolved through 

 selection, the comb-making habit of the social hymenop- 

 tera has surely arisen in the same way and not through 

 the operation of an entirely different set of causes." 



After having ennunciated so clearly and convincingly 

 the claims of instinct to account for the wonderful organ- 

 ization of social hymenoptera, the elaborate cocoons of 

 moths, etc., it does seem a bold flight which denies all 

 instinct to the birds wiiich, we are assured, must acquire 

 by experience what is good and what is bad to eat. 



Is it instinct or is it acquired intelligence that has 

 taught the weaver birds to build their pendant nests? 

 If it is due to intelligence acquired during life time, how 

 is it that the inexperience of young couples does not 

 lead them astray in this important function? If it is in- 

 telligence that is relied on, how is it that swallows so 

 often build their mud nests in unsuitable jjositions such 

 as under iron roofs, with the result that they fall down, 

 and yet are often rebuilt under identically similar con- 

 ditions? If it be instinct, as I should sux-)pose, that 

 teaches them to build, it would naturally fail to teach 

 them the inappropriateness of building under iron roof- 

 ing. The inexi^erience of young birds in the matter of 



