v COLOURS OF ANIMALS 345 



abundance j the species with small and inconspicuous flowers 

 greatly preponderate ; and the flowering season of each kind 

 being of short duration, they rarely produce any marked 

 effect of colour amid the vast masses of foliage which sur- 

 round them. An experienced collector in the Eastern tropics 

 once told me that although a single mountain in Java had 

 produced three hundred species of Orchidese, only about 2 

 per cent of the whole were sufficiently ornamental or showy 

 to be worth sending home as a commercial speculation. The 

 Alpine meadows and rock-slopes, the open plains of the Cape 

 of Good Hope or of Australia, and the flower -prairies of 

 North America, offer an amount and variety of floral colour 

 which can certainly not be surpassed, even if it can be 

 equalled, between the tropics. 



It appears, therefore, that we may dismiss the theory that 

 the development of colour in nature is directly dependent on, 

 and in any way proportioned to, the amount of solar heat and 

 light, as entirely unsupported by facts. Strange to say, how- 

 ever, there are some rare and little-known phenomena which 

 prove that in exceptional cases light does directly affect the 

 colours of natural objects, and it will be as well to consider 

 these before passing on to other matters. 



Changes of Colour in Animals produced by Coloured Light 

 A few years ago Mr. T. W. Wood called attention to the 

 curious changes in the colour of the chrysalis of the small 

 cabbage -butterfly (Pontia rapse) when the caterpillars, just 

 before their change, were confined in boxes lined with 

 different tints. Thus in black boxes they were very dark, in 

 white boxes nearly white ; and he further showed that similar 

 changes occurred in a state of nature, chrysalises fixed against 

 a whitewashed wall being nearly white, against a red brick 

 wall reddish, against a pitched pailing nearly black. It has 

 also been observed that the cocoon of the emperor-moth is 

 either white or brown, according to the colours surrounding 

 it. But the most extraordinary example of this kind of 

 change is that furnished by the chrysalis of an African 

 butterfly (Papilio Nireus), observed at the Cape by Mrs. 

 Barber, and described (with a coloured plate) in the Transac- 

 tions of the Entomological Society, 1874, p. 519. 



