162 THE WORLD OF LIFE CHAP. 



sometimes very great in closely allied species) should have 

 been acquired for the sole purpose of fighting with each other 

 or with an enemy. But as these animals all possess markings 

 on the head and body which can only be interpreted as 

 recognition-marks especially serviceable while in motion, it 

 seems quite natural that the horns should have been modified 

 to serve the same purpose while the animals are at rest, or 

 when their bodies are wholly and their faces partially con- 

 cealed by the grasses or bushes around them. 



The essential character of directive or recognition-marks 

 is strikingly shown by one of the best known of the African 

 antelopes the springbok which in the early days of the 

 Cape Colony swarmed over the whole of South Africa, even 

 in the vicinity of Cape Town. Its chief feature is thus 

 described in Chambers's Encyclopaedia : 



" Two curious folds of skin ascend from the root of the tail to 

 near the middle of the back ; they are closed when the animal is 

 at rest, but when leaping or running they open out and disclose a 

 large white patch, which is otherwise concealed." 



We have here a structural peculiarity leading to the 

 production of a distinctive white patch on a prominent part 

 of the body, which patch is concealed when not required and 

 when it might be dangerous, and only exhibited in the 

 presence of some real or imaginary danger, for the spring- 

 bok is said to be one of the most timid and cautious of all 

 animals. This curious feature is more remarkable, and more 

 clearly a proof of a mark designed to be seen, than even our 

 rabbit's upturned tail when running, which has been termed 

 the w signal flag of danger," and in moonlight or evening 

 twilight serves, on the approach of an enemy, to guide the 

 young, or those farthest from home, towards the family 

 burrow. 



Recognition- Marks in Birds 



A large number of birds also possess these two kinds 

 of recognition-markings, the one to be seen when resting 

 or feeding, the other only during flight. As good examples 

 of these I give figures of the head and wings of three allied 

 species of stone-curlews, inhabiting Eastern Australia, the 

 Malay Archipelago, and India, respectively, whose ranges 



