THE MASTER INSTINCT 
but if it had, not later than June, they would prob- 
ably have built still another nest. The phoebes usu- 
ally rear two broods in a season when all goes well 
with them. It is to build the nest and rear the young 
that they have made the long and hazardous jour- 
ney from our Southland, or even from Central 
America, and it is this that will cause them to make 
it every spring as long as they live. It is this that 
impels myriads of other small birds and water-fowl 
to make the same trip from the Far South, braving 
storms and winds and other perils by land and sea. 
To beget progeny that will in time reproduce them- 
selves is the unconscious and unquenchable motive 
that actuates them all. This same motive impels 
the golden plover to make its marvelous flight from 
the plains of Patagonia to the Arctic Circle in 
Alaska, a distance of nearly half the circumference 
of the globe, crossing oceans without arest. It sends 
the European migrants across the Mediterranean 
from Africa to France, many of them so fatigued on 
reaching land that they fall an easy prey to man and 
beast. 
It is the impelling force of this motive or instinct 
that sends the fish up the streams and rivers in the 
spring, making the waters alive with denizens from 
the sea, impelling the salmon to leap falls, or, failing 
to scale them, to keep up the effort till they die from 
exhaustion. The breeding-instinct is the ruler of life. 
It asks no questions, it requires no guarantee, it 
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