300 peesident's addeess. 



the material universe are insufficient " to account for the whole 

 cycle of natural phenomena. 



One of the most interesting subjects treated by Mr. Wallace 

 in these Essays is that of Mimicry, or Protective Resemblance, 

 a phenomenon first distinctly noticed, I believe, by Mr. Bates in 

 his valuable work, " The Naturalist on the Amazons," and by 

 him referred to the action of Natural Selection. The most pro- 

 minent instance given by this author is that of certain butterflies 

 {Leptalides) of South America, which closely imitate in flight 

 and general appearance an essentially different family, the Heli- 

 conidce ; these latter being apparently protected from the attacks 

 of insectivorous birds by their overpowering odour, which is, 

 however, not shared by the Leptalides. The facts here are not 

 disputed, and Mr. Wallace adds, from his own experience, many 

 striking examples, some of them even more wonderful, from the 

 closeness and grotesqueness of mimetic resemblance, as for in- 

 stance in the cases of the so-called stick and leaf insects. The 

 disputed point, however, is the origin of these extraordinary re- 

 semblances. Mr. Bates and Mr. Wallace hold that they have 

 arisen by the long-continued action of Natural Selection on suc- 

 cessive small variations, each bringing the animal more near to 

 the stage of perfect mimicry, and thus affording a continually 

 increasing protection. The difficulty here seems to lie in the 

 first stages, where the protection afforded must in all probability 

 be small ; how small it is impossible to say : Mr. Wallace, how- 

 ever, believes that quite a profitable degree of modification may 

 occur as a first step, a belief in which he is opposed by various 

 other writers. In considering this subject, it must be remem- 

 bered that we have to account not only for cases of extreme and 

 grotesque Mimicry which appear to be more prevalent in tropi- 

 cal climates than in our own, but for a very wide spread mimetic 

 tendency, which seems indeed to exist more or less throughout 

 the whole animal creation ; and it seems to me that Natural Se- 

 lection, though not offering in every point an entirely satisfactory 

 solution, is at least the only principle at present known to us 

 which renders the matter at all intelligible. 



Mr. Mivart tells us that he was at one time disposed to accept 



