128 BIEDS 



time of their coming." There seems, that is to say, to 

 be a kind of planetary precision in these mighty move- 

 ments, and there is a consequent danger of over-simplify- 

 ing the problem. It would be presumptuous so much as 

 to attempt to solve this deep mystery in a note, but our 

 knowledge that the young birds more frequently lead the 

 autumn movement in advance of the adults (as they are 

 the last to arrive in spring), does not suggest that migra- 

 tion originated in a mere choice of nesting sites. Food 

 and reproduction undoubtedly play their parts, but these 

 are surely only part constituents of a whole phenomenon 

 whose grandeur seems to baffle our searchings. Pro- 

 fessor Thomson's theory is discussed with his usual power, 

 breadth of mind, temperate fairness, and beauty of ex- 

 pression, both in " The Wonder of Life " and the 

 " Biology of the Seasons," and, quite apart from its 

 biological value, it has the poetic advantage of correlating 

 this rush of " infinite wings," this rhythmic swing be- 

 tween exile and home, repose and labour, expenditure 

 and repair, " breeding and nesting," and " feeding and 

 resting," with a vast original disturbance and change in 

 inanimate nature. His theory does not impoverish our 

 sense of awe at this miracle of travel, and our deeper 

 senses are no bad practical guides. Lastly, Mr. Stowell 

 objects that Professor Thomson's theory postulates a 

 " sudden revulsion." But " mutations " (which Samuel 

 Butler rightly called ' ' happy thoughts ' ' and are really 

 what we should call inspirations born in the germ-cells) 

 are well established in modern biology. Certainly they 

 modify the Darwinian idea that variations are ' ' numerous , 

 successive, and slight," but the evidence for sudden leaps 

 and bounds in natural progress is by no means scanty (see 

 De Vries, Bateson, etc.). Man himself has been called 

 a mutation in his origin viz., a " prepotent anthropoid 

 genius." 



