150 REV. W. SERLE ON 
years, and yet they migrate. Palmén maintains “that 
originally birds lived in latitudes which supplied them through- 
out the year with everything necessary to their existence ; 
that in progress of time some of them accidentally came to 
stray so far beyond the northern limits of their homes, that on 
the approach of winter they were compelled to retrace their 
path in order not to succumb to cold and hunger; that a 
habit of migrating was developed from such accidental 
erratic wanderings, and that the habit, together with the 
experiences made on these journeys, had been passed on by 
inheritance from the old birds to the young.” We do not 
believe that such phenomena were the result of accidents. 
Seebohm, who did not always hold the same idea, said 
latterly :—‘ The origin of migration probably does not date 
back to a period before the glacial epoch. As birds gradually 
began to increase and multiply to an extent sufficient to 
produce a struggle for existence in the form of a fight for 
food, they seem to have adopted a custom, which they still 
retain, of leading away or driving away their families every 
autumn to seek food and a home elsewhere, As the circle of 
bird-life constantly widened, in due time the abundance of food 
tempted many birds to stray into the Arctic regions to breed 
during the long summers of those climates at that period. 
Probably during the darkest months of mid-winter—if the 
cool season of the pre-glacial period may be called winter 
—gome local migration took place and birds wandered back 
again for a month or two into the adjoining districts, but 
these little journeys can scarcely be dignified with the name 
of migration. Then in process of time winters became 
severe at the poles, and birds had to learn to migrate. Then 
came the glacial period, when birds were driven south before 
ice-fields and crowded into the tropics of Asia and Africa. 
After the glacial period had passed its meridian and the 
edge of the ice gradually retreated, so did the birds, leaving 
here and there colonies which formed tropical allies.” 
Wallace, a living naturalist of considerable eminence, says :-— 
“ Migration is an exaggeration of a habit common to all 
locomotive animals of moving about in search of food, 
but greatly exaggerated in the case of birds by their power 
of flight and by the necessity of procuring a large amount 
