418 PHOTOGRAPHS OF BURCHELL’S AND WAHLBERG'S QUAGGAS. [ Apr. 27, 
marked in the same way, but one is remote and the other closer 
at hand. To detect this the Zebra must be regarded from a 
moderate distance and not at so great a distance that the stripes 
blend into a uniform grey, as is said to be the case*. 
Text-fig. 50. 
Sevag * 
= 
a 
x 
a 
Diagram of one of the northern races of Hquws quagga, to show how variation in 
the direction and the width of the stripes contributes to the procryptic effect 
of the pattern. 
‘Other striped species of the genus Hquus exhibit similar phe- 
nomena, but none shows the division down the middle of the side 
which is so marked a characteristic of the existing forms of 
LH. quagga. In £. zebra and £. foai the change of direction does 
not take place until the hind-quarters are reached; but on this 
area in /, zebra there is not only a difference in direction of the 
stripes, but an extraordinary difference in their size, so that the 
greatest possible contrast is secured. Finally, of all the Zebras 
HL. grevyiis perhaps the most uniformly striped, but the small 
striped head is severed from the small striped shoulder by the 
neck, the stripes of which, at least in its posterior half, are usually 
of comparatively enormous width. But in the foal of this species 
what may be described as an attempt at the optical division of the 
body into two halves is made. This is effected not by an altera- 
tion in the direction of the stripes, but by an alteration in their 
* There is, in my opinion, very little doubt that the sharp contrast im colour 
between the black anterior and white posterior parts of the body of the Malayan 
Tapir (Lapirus indicus) has a procryptic significance similar to that achieved by 
the alteration in the direction of the stripes seen in existing forms of Quaggas. 
