26 EXPOSED AND CONCEALED ANIMALS 



forms, it may be noted in the first place that 

 while the green colouring matter of plants 

 effects its characteristic reaction, the chlorophyll 

 reaction, by reason of its exposure to sunlight, 

 the respiratory pigments of animals which pro- 

 mote another kind of gaseous interchange, are 

 enclosed in blood-vessels and sinuses, generally 

 concealed from the light by an opaque skin, and 

 always independent of the light, even though the 

 skin should happen to be transparent. 



As a second example to illustrate broadly the 

 essential cryptotaxis (tendency to concealment) 

 of animals, may be mentioned the well-known 

 fact that even among the higher vertebrates 

 many birds and most mammals are, in the wild 

 state, concealed from view by their protective 

 coloration. Of course this does not in itself 

 shelter them from the sun ; the environment 

 provides the cover ; but it protects them from 

 the visual acuity of their enemies, many of 

 which are notoriously cryptotactic. A common 

 method of shooting wild animals, for sport or 

 for food, is to lie in wait at night concealed 

 behind an ambush within range of a water-hole 

 where they will come to drink. The largest 

 mammals, whether carnivorous or herbivorous, 

 such as the tiger, elephant, and giraffe, are 

 known to be almost invisible when at rest in 

 the forest, jungle, and high grass which they 

 frequent in the daytime. In Ceylon, the rounded 



