114 SECRETS OF ANIMAL LIFE 
by the temperature and oxygenation of the water 
and so on; they are impelled by an internal spur— 
a seasonal change of constitution; but in thinking 
over this return to their natal waters, or to waters 
similar in character, we probably go far wrong in 
the direction of false simplicity if we do not recog- 
nize in the salmon struggling against the stream a 
bent bow that is more than material. We mean that 
in its way the salmon is a personality—a piscine 
personality if you will—with a life not only of 
contracting and relaxing, digestion and combustion, 
and so on, but a life of feeling and willing besides, 
the two making one. And just as the salmon 
illustrates an intensely active genetic impulse, the 
expression of physiological and psychical enregistra- 
tions both racial and personal, so in these wind- 
borne clouds of winged fruits and parachuted seeds 
we see on a very different level and with little hint 
of “the bent bow’”’ the same fascinating problem 
of adaptations which secure the continuance of the 
race from generation to generation. 
The familiar withering and fall of the leaves 
can never fail to excite the interest of those who 
keep alive the curious spirit. What busy synthetic 
laboratories they have been all the summer through, 
what abundance of complex carbon compounds 
have they manufactured! and now the laboratory 
furnishings are worn out and the leaves must die. 
But there is high art in their dying; for there is a 
migration of almost all that is valuable from leaf to 
stem, so that little more than waste is left to fall; 
