I20 NATURAL HISTORY ESSAYS 



dun-coloured fringe on the throat,^ The body colour 

 in summer is also of a less pronounced grey than in 

 winter, being tinged with yellow; the brown tuft 

 of hair on the forehead remains unaltered at all 

 seasons. The addax thus follows the law that in 

 animals of mutable coloration {e.£'., Arctic fox, 

 changeable hare) the summer coat is brown or 

 rufous and the winter one grey or white. 



Widely distributed throughout the Sahara from 

 Senegal to Kordofan, the northward range of the 

 addax appears to ^e limited by the Chott Djereed 

 and its sister lakes ; the southward limit is unknown, 

 though Denham and Clapperton presented to the 

 British Museum two ununited horns which they had 

 obtained during their Central African expedition of 

 1822-24. This antelope was formerly found in 

 Central Tunisia ; its present head-quarters are in 

 the Erg country — a vast tract of the Sahara which 

 continues league after league as a wilderness of rollinsf 

 sandhills, smooth as olass, almost entirely barren, 

 and utterly desolate and silent. The rare traveller 

 sinks ankle-deep in the yielding surface and may 

 lose his way in the shifting sand ; the route is 

 scantily indicated by mounds of pebbles, or by 



1 liensliaw: Zoologist, October, 1902. Six photoj^raphs illustrating 

 the seasonal clianges of the addax were taken by tlie present writer a 

 few years aj^o, of which two were published in tlie Zoolor/i.tf and two 

 more are reproduced in tlie present work. The winter coat appears to 

 fall out irre;.Milarly. coniniencinj,' on either side of the spine, and spreading 

 downwards from several centres. The kind reception accorded to the 

 photographs by the Press seems to indicate that the inethod of dehiscence 

 of the hair had not hitherto been investigated. 



