216 ENVIRONMENT 



tropical sun : their colour is a hereditary trait, 

 but it results from a pigment which (as already 

 mentioned) may be acquired in some degree by 

 a European who resides for many years in the 

 tropics. If we follow the representatives of the 

 Equidae that occur wild in Asia and Africa, we find 

 that colour markings become brighter and cover a 

 larger surface of the body as we approach the 

 equator from either north or south. The wild horses 

 of Mongolia and the Asiatic deserts are striped 

 indistinctly on the legs. In the ass of Nubia and 

 Abyssinia stripes are developed on the shoulders 

 as well as on the legs, and become more con- 

 spicuous. They cover the body of the tropical 

 zebras, but disappear from the legs and under 

 surface of the zebra (Chapman's) of the Orange 

 River, and were limited to part of the upper 

 surface of the (now extinct) quagga, still farther 

 south. Brilliancy is a conspicuous feature of 

 tropical insects and flowers. Tropical birds are 

 also generally distinguished by brightness of 

 colour, as well as by the length of their beaks 

 and tails. On the other hand, it is in the temperate 

 regions that birds develop their sweetness of 

 song. There is no obvious connection between 

 coolness and vocal capacity : nor is there 

 between aridity and the spiny growths that are 

 thrown out by plants and by some lizards in 

 widely separated 1 desert countries. Yet in both 

 cases we may feel sure that a connection exists. 

 Doctors are well aware that the recuperative 

 virtues of health resorts are frequently limited, 

 very unaccountably, within quite small areas. 

 The influence of environment, by promoting or 



1 In similar environments the ostrich and the llama have 

 developed a curious similarity of form. Darwinists ascribe this to 

 the effect of similar selective influences. But it will corroborate 

 the existence of more subtle influences to those who have been led 

 by other coincidences to believe in them. 



