6S2 DR. J. c. MOTTKAM ON 



look upon the zebra as one of the most difficult wild animals to 

 pick up. 



^ Of the zebras, E. burchelli presents between the stripes con- 

 siderable obliterative shading, as well as faint stripes of buflf. 

 E. grevyi also has some obliterative shading, E. zebra very little, 

 and E. burchelli granti none at all. Complete absence is, however, 

 not uncommonly seen in all the species. 



Thayer, in ' Concealing Coloration in the Animal Kingdom,' 

 looks upon the striped coat of this animal as an obliterative 

 picture-pattern of rank grasses and tree-stems : it is noteworthy 

 that he makes no mention of the absence of obliterative shading, 

 which he elsewhere insists always forms the canvas for picture- 

 painting. If, however, examination be made of the pattern to 

 be seen on viewing a zebra from behind (see text-fig. 2, 1.), it is 

 at once evident that this does not represent a picture-painting of 

 reeds, herbage or trees. On the other hand, it illustrates in a 

 remarkable way obliterative shading by means of pattern. Text- 

 fig. 2, 2, is a modelled drawing of the same view with the stripes 

 omitted, the lighting being from above, and shows the major 

 shadows which are cast. On comparing these two figures it can 

 be seen that in the high lights, the stripes are broad, and that as 

 one passes into the shadows, they fade away : where the high 

 light strikes the hocks the bands are broad, whereas below the 

 hocks where the leg is in the shadovp, the stripes are narrow. 

 The striping on the tail even falls into line, as shown in text- 

 fig. 2, 4, 5._ 



The Guineafowl {Numida meleagr is).— This bird illustrates 

 obliterative shading by means of white spots on an even blue-grey 

 background (text-fig. 3, 1, bottom right-hand square). On the 

 back the white spots are small, but become larger as one 

 passes to the ventral aspect, where they are four times the 

 diameter of those on the back. In some species the wings are 

 covered with a series of short white bars, narrow on the back 

 and broader below, as the wing lies covering the body during 

 rest. These markings on the bird blend at a comparatively 

 short distance ; within the blending distance the bh'd appears 

 conspicuous, beyond, difficult to see. The bird lives in open 

 countr}^, and there does not appear to be anything in its surround- 

 ings which this pattern emulates. 



The Cheetah {Gyncelurus jubatus). — The pattern, as shown in 

 text-fig. 3, 1, bottom left-hand square, consists of Mack spots on 

 a pale fawn background : the background presents either no 

 obliterative shading or very slight ; the spots are close together 

 on the back, gi-adually becoming more distant towards the ven- 

 tral surface, which is hidden b}' a fringe of long hairs pr-ojecting 

 downwards from the flank. 



The Serval {Felis served) jDresents a similar pattern to the 

 Cheetah except that in the dorsal region, spots are replaced by 

 short bars. This kind of pattern is commonly seen in the 

 Civets. 



