So IN BIRD LAND. 



Allen's valuable paper on the " Origin of the In • 

 stinct of Migration in Birds." The extract is taken 

 from an article by Frank M. Chapman, published in 

 "The Auk" for January, 1894 ; " Nothing is doubtless 

 more thoroughly established than that a warm tem- 

 perate or sub-tropical climate prevailed down to the 

 close of the Tertiary epoch, nearly to the Northern 

 Pole, and that climate was previously everywhere so 

 far equable that the necessity for migration can 

 hardly be supposed to have existed. With the later 

 refrigeration of the northern regions, bird life must 

 have been crowded thence toward the tropics, and 

 the struggle for life thereby greatly intensified. The 

 less yielding forms may have become extinct ; those 

 less sensitive to climatic change would seek to extend 

 the boundaries of their range by a slight removal 

 northward during the milder intervals of summer, 

 only, however, to be forced back again by the recur- 

 rence of winter. Such migration must have been at 

 first 'incipient and gradual,' extending and strength- 

 ening as the cold wave receded, and opened up a 

 wider area within which existence in summer became 

 possible. What was at first a forced migration 

 would become habitual, and through the heredity 

 of habit give rise to that wonderful faculty which 

 we term the instinct of migration." The reader's 

 attention is also directed to Mr. Chapman's own 

 article in the number of " The Auk " indicated. 



It may be asked why some species remain in 

 torrid and temperate climates, while others wing 

 their way to the far north, even beyond the boun- 



