American Prong-Horn 
haps come in view, and once more stand and gaze at the in- 
truder.”’ 
The wonderful watchfulness of the antelope is due naturally 
to its continual exposure in the open country in which it lives 
and the necessity of being ever prepared to get a clear start of 
the wolves or such other enemies as may harass it, against 
which flight is its only safeguard. 
Like many other animals that habitually associate in flocks, 
the antelope has in its two white rump patches conspicuous 
‘recognition marks,’’ as they have been termed, by which, ac- 
cording to Wallace’s theory, individuals can at a glance recog- 
nize their own kind, even though at a considerable distance. The 
rump patches of the antelope, however, are different from those 
of other ruminants and are of much more importance to the 
animal. Ernest Seton-Thompson, writing of this matter in The 
Century Magazine, says: ‘‘Some years ago, while riding across 
the upland prairie of the Yellowstone, I noticed certain white 
specks in the far distance. They showed and disappeared seve- 
ral times and then began moving southward. Then, in another 
direction, I discovered other white specks which also seemed to 
flash and disappear. A glass showed them to be antelope, but 
it did not wholly explain the flashing or the moving which ul- 
timately united the two bands. I made note of the fact, but 
found no explanation until the opportunity came to study the 
antelope in the Washington Zoo.” He goes on to explain how 
the approach of a dog to the enclosure of the captive animals 
caused them to elevate the hair all over their rump patches. 
‘‘The wild antelope habit is to raise the head while grazing to 
keep a sharp lookout for danger, and these captives kept up 
the practice of the race. The first that did so saw the dog. It 
uttered no sound, but gazed at the wolfish-looking intruder and 
all the long white hairs of the rump patch were raised with a 
jerk that made the patch flash in the sun like a tin pan. Every- 
one of the grazing antelopes saw the flash, repeated it instantly 
and raised his head to gaze in the direction in which the first 
was gazing. At the same time I noticed on the wind a _pecu- 
liar musky smell—a smell that certainly came from the antelope.”’ 
Subsequent investigation showed the presence of a musk gland 
in the centre of the rump patch and a mass of muscle connected 
with it and with the bases of the white hairs. This completed 
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