KECOGNITION-MAEKS 175 



" 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 pro- 

 duction of a distinctive white patch on a prominent part of 

 the body, which patch is concealed Avhen not required and 

 when it might be dangerous, and only exhibited in the pres- 

 ence of some real or imaginary danger, for the sj^ringbok 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 he seen, than even our rabbit's 

 upturned tail wdien running, wdiich has been termed the 

 *^ signal Hag 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 feed- 

 ing, 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 sometimes 

 overlap, and which are no doubt descended from a common 

 ancestor. The head of each exhibits different markiuirs, bv 

 which they can be easily distingTiished while feeding on the 

 ground ; while the bolder markings on the wings enable them 

 to keep together during their wanderings or migrations (Figs. 

 36, 37, and 38). 



Markings of this character, though varied almost infinitely, 

 occur in all classes of the hioher animals, and very mucli 

 in proportion as their mode of life requires them. When con- 

 cealment is of more importance, then the recognition is made 

 effective by differences of shape or of motions and attitudes, 



