50 
énd; but uncons¢iously, or, in other words, by instinct. In 
abstaining from setting forth new theories, I have been guided by 
the conviction, rendered firmer with increasing knowledge of the 
phenomena, that what at present has been ascertained in reference 
to the migration of birds furnishes us with no clue by the aid of 
which we are enabled to penetrate the depths of this wondrous 
mystery. The life of man is too short for the complete exploration 
of this inexhaustible field, and one can only regret that one is 
unable to-start afresh with observations and enquiries from the 
standpoint which one has reached at its close.”’ 
Le 
3 eter Wem we be GS 
ies . 
te ed ad ts 
