240 THE WONDER OF LIFE 



into any other, though some prawns are more susceptible 

 than others. ' Once changed, the colour of the Hippolyte, 

 even in the most obstinate, becomes plastic, and can be 

 changed with astonishing rapidity, sometimes in ten 

 minutes '. 



According to Minkiewiez, what it seems to come to is 

 this. In a green environment, the spider-crab becomes 

 positively susceptible to green, and negative in relation 

 to other colours. It will disguise itself in such green as it 

 can find growing on the green surfaces. It does not choose 

 its disguise. When it is transferred to an aquarium half 

 red and half green, it goes to the green half, not because its 

 disguise is green, but because it is itself attracted by green. 

 It does not choose its environment. In a dark aquarium 

 the crab may make itself conspicuous by putting on pieces 

 of Hght-coloured paper instead of black paper, for any 

 colour is more attractive than black, which has no influence 

 at all. 



The behaviour of the spider-crab in its self-concealment 

 is composed of two parts. In the first place, it is drawn or 

 driven towards certain coloured surfaces, according to the 

 sum of the given conditions. Once there, and in touch 

 with material — usually seaweed — it begins, in the second 

 place, to cover itself, one set of tactile impressions provoking 

 certain movements of the claws, which lead to tactile impres- 

 sions of the mouth parts and further movements — and so 

 on, until the whole routine is accomplished. We have 

 given this case in some detail because it illustrates the work 

 of the modern school, who rightly believe in pushing physio- 

 logical interpretations as far as they wUl go before invoking 

 an ' efficient consciousness ' or the hke. 



In Summary. — As regards the theory of instinct, there 



