AGGRESSIVE RESEMBLANCES, ETC. 79 



human and purposeful. Many substances, as hydroids, 

 sponges, Polyzoa, and weeds of many kinds and 

 colours, are thus used, but these various substances 

 are nearly always symmetrically placed on corre- 

 sponding parts of the body, and particularly long, 

 plume-like pieces are fixed on the head, sticking up 

 from it. . . . Not only are all these complicated 

 processes gone through at night as well as by day, 

 but a Stenorhynchus if cleaned and deprived of sight 

 will immediately begin to clothe itself again, with the 

 same care and precision as before.' ^ Bateson states 

 that Stenorhynchus does not betray any disposition to 

 remain in an environment which harmonizes with its 

 dress. 



Adventitious Colouring 



The protective colouring of many animals may be 

 due to the food in some part of the digestive tract, 

 seen through the transparent body. This is impor- 

 tant in many transparent caterpillars, such as the 

 NoctU(s, and probably in many marine organisms. If 

 a larva, such as that of the Angle-shades {Phlogoi:)hora 

 meticnlosa) , be fed on the orange- coloured marginal 

 florets of the marigold, the passage of food along the 

 alimentary canal can be distinctly traced by the pro- 

 gressive change in the colour of the caterpillar. 



The green colour of the blood of most larvae is 



* Journ. Mar. Biol. Assoc, New Series, vol. i. No. 2, Oct. 1889, pp. 

 213-14. 



