540 THE ZOOLOGIST. 



horses (Phyllopteryx sp.) " closely resemble the colour of sea- 

 weeds to which they attach themselves, while the filamentous 

 appendages of their spines appear as if they were actually a part 

 of the vegetable growth."* The Dragonfly larva "trusts chiefly 

 to its sombre colouration and its motionless attitude. The larva 

 clinging to a stem in the shady recesses of water-weeds is not 

 easily distinguished, and the absence of movement removes the 

 chief risk of discovery." f Many caterpillars resort to the bark 

 of trees, with which their colour and often notched, knotted, or 

 spotted bodies closely assimilate. That this is a form of active 

 mimicry may be gleaned from the remarks of a British entomo- 

 logist :—'' A number of these mimics of the insect world never 

 venture to feed by day, but take in their quantum of provision 

 during the dark hours, and practise their deceptions during the 

 day." I Active mimicry may also explain resemblances which 

 Weismann is very emphatic in denying as due to " external 

 influences." " If a caterpillar, which hides itself by day in the 

 crevices of the bark, possesses the same colour as the latter, 

 whilst other caterpillars which rest on leaves are of a green 

 colour, these facts cannot be explained as the result of the direct 

 influence of the bark and leaves. And it would be even less 

 possible to explain upon the same principle all the details of 

 marking and colour by which these animals gain still further 

 protection. If the upper side of the upper wings of certain 

 moths is grey like the stone on which they rest by day, while in 

 butterflies the under side of both wings which are exposed during 

 rest exhibits analogous protective colours, these facts cannot be 

 due to the direct influence of the surroundings which are 

 resembled ; but, if they have arisen in any natural manner, they 

 must have been indirect^ produced by the surroundings." § 

 These last remarks appear to be obscure. Surely, to make the 

 proposition clear, some explanation should have been given as to 

 what is meant to be differentiated between " cannot be due to 

 the direct influence of the surroundings," and " must have been 

 indirectly produced by the surroundings." And therefore, per- 



* ' Eoyal Nat. Hist.' vol. v. p. 426. 



| L. C. Miall, ' Nat. Hist. Aquatic Insects,' p. 332. 



+ "W. Furneaux, ' Butterflies and Moths (British),' pp. 31-2. 



§ ' Lectures on Heredity,' &c, 2nd edit., Eng. transl., vol. i. p. 409. 



