DIFFERENTIATION, MIGRATION, AND MIMICRY. 377 



hold good in the varying storms of the Atlantic, still less in the 

 vast stretch of stormy and landless ocean crossed by the Bronze 

 Cuckoo (Chrysococcyx lucidus) in its passage from New Guinea 

 to New Zealand. Professor Palmen ascribes the due performance 

 of the flight to experience, but this is not confirmed by field 

 observers. He assumes that the flights are led by the oldest and 

 strongest ; but observation by Herr Gatke has shown that among 

 migrants, as the young and old journey apart and by different 

 routes, the former can have had no experience. All ornithologists 

 are aware that the parent Cuckoos leave this country long before 

 their young ones are hatched by their foster-parents. The sense 

 of sight cannot guide birds which travel by night, or span oceans 

 or continents in a single flight. In noticing all the phenomena 

 of migration, there yet remains a vast untilled region for the field- 

 naturalist. 



What Professor Newton terms " the sense of direction, uncon- 

 sciously exercised," is the nearest approach yet made to a solution 

 of the problem. He remarks how vastly the sense of direction 

 varies in human beings, contrasting its absence in the dwellers in 

 towns compared with the power of the shepherd and the country- 

 man, and, infinitely more, with the power of the savage or the 

 Arab. He adduces the experience of Middendorff among the 

 Samojeds, who know how to reach their goal by the shortest way 

 through places wholly strange to them. He had known it among 

 dogs and horses (as we may constantly perceive), but was surprised 

 to find the same incomprehensible animal -faculty unweakened 

 among uncivilised men. Nor could the Samojeds understand his 

 enquiry, how they did it ? They disarmed him by the question, 

 How now does the Arctic Fox find its way aright on the Tundra, 

 and never go astray ? and Middendorff adds, " I was thrown back 

 on the unconscious performance of an inherited animal-faculty "; 

 and so are we ! 



There is one more kind of migration, on which we know 

 nothing, and where the field-naturalist has still abundant scope 

 for the exercise of observation. I mean what is called exceptional 

 migration, not the mere wanderings of waifs and strays, nor yet 

 the uncertain travels of some species, as the Crossbill in search 

 of food, but the colonising parties of many gregarious species, 

 which generally, so far as we know in our own hemisphere, travel 

 from east to west, or from south-east to north-west. Such are 



ZOOLOGIST, — OCTOBER, 1893. 2g 



