174 BOMBAY DUCKS 
the legs of one antelope are half an inch longer than 
those of another, the former has certainly, other things 
being equal, an advantage in the struggle for existence. 
But other things are so rarely equal. A slight advan- 
tage, such as this, may be easily counterbalanced by 
luck, 
Two antelopes may be feeding together, when they 
are seen by a beast of prey. They fly together, and 
the faster one soon begins to lead, but he happens to 
stumble into a quagmire; his neighbour profits by his 
mistake and takes another course, so that the poor 
creature who is floundering in the soft mud is fallen 
upon and devoured by the pursuer, while its less speedy 
companion escapes. 
On the other hand, it is easy to see how a little extra 
brain-power can assist a species. A cute antelope may 
not be particularly fleet, nor very strong, but he will be 
careful to choose as feeding grounds places where he 
cannot be surprised, and, when he is chased, he will 
follow the course best adapted to his mode of pro- 
gression; carefully avoiding all soft ground, he will profit 
to the uttermost by his knowledge of the locality ; he 
will run, as far as possible, in a straight line, so that his 
pursuer will not be able to cut off corners. 
Hundreds of athletic species, which are known to us 
only as fossils, might to-day be living, if, when the 
struggle for existence began to press hardly upon them, 
they had had the wit to build boats and sail away to 
some corner of the earth where the competition was a 
little less keen. Every organ of every animal is subject 
to variation, and the brain forms no exception. 
