MIGEATION. 39 



(E) From extreme N. of Siberia, mounts the Yenesei to Lake Baikal, and so 

 passes into Mongolia. 



(F) From extreme N. of Siberia, ascends the Lena, and striking the Upper 

 Amoor, reaches the Sea of Japan. 



(G) From the eastern portion of Siberia to the Sea of Japan. 



(0) From Kamschatka to the Sea of Japan. 



(X) Starting from Greenland and Iceland, passes by the Faeroes to the British 

 Islands, and so, joining {B) and (C), runs down the French coast. 



These are the main routes, while nearly all river courses form minor routes. 



Return to former haunts inexplicable. But lay down the paths of migratory 

 birds, observe their comings and goings, or strive, as we will, to account for the 

 impulse which urges them forward, there still remains for consideration the most 

 marvellous thing of all. How do the birds find their way so unerringly from 

 such immense distances ? This seems to be by far the most inexplicable part of 

 the matter. 



Year after year the migratory Wagtail will build her nest in the accustomed 

 spot, and year after year the migratory Cuckoo will deposit her eggs in that nest, 

 and yet in each interval of time the former may have passed some months on the 

 shores of the Mediterranean, and the latter, absent for a still longer period, may 

 have wandered into the heart of Africa (absolute proof and identity of particular 

 birds is, of course, wanting; but if that objection be raised, the circumstance 

 becomes still more puzzling, for then we have to account for some mode of com- 

 municating precise information by one bird to another). Solution of this mystery 

 does not lie in the " homing '' faculty, for this depends on a knowledge of land- 

 marks obtained by sight, and sight only is the sense which directs pigeons, while 

 sight alone can hardly afford much aid to birds which at one stretch transport 

 themselves across the breadth of Europe, or even traverse more than 1,000 miles 

 of open ocean, to say nothing of those birds which perform their migrations by 

 night. 



Instinct is no explanation of this wonderful faculty; it is an evasion of the 

 difficulty. Herr Palm^n ascribes the performance of the flight to experience 

 where migrants are led by the older and the stronger birds. It is likely that the 

 strongest lead the flock, but not necessarily the oldest. Besides, many birds do 

 not migrate in flocks ; for example, while swallows do leave our shores in large 

 companies, the majority of summer visitors slip away almost unobserved ap- 

 parently without concert with others. Temminck states that among migrants 

 the young and the old always journey apart, and most generally by different 

 routes. The former can have no " experience," and yet the greater number of 

 them arrive safely. The sense of sight, essential to a knowledge of landmarks, 

 is insufficient to account for the success that attends birds which travel by night, 

 or in a single flight span oceans or continents. Yet without it the idea of 

 "experience'' cannot be substantiated. We may admit that inherited but un- 

 conscious experience, which is really all that can be meant by instinct, is a factor 

 in the whole matter, certainly, as Mr. Wallace seems to have proved, in origi- 

 nating the migratory impulse; but yet every aspect of the question is fraught 



