CASES OF ADAPTATION 149 



latitude as Scarborough. Most of the migratory birds from 

 Scandinavia and Arctic Europe pass along the coasts of 

 the German Ocean, and the lighthouse on Heligoland serves 

 as a guide, and the island itself as a resting-place during bad 

 weather. Mr. Seebohm's account of what he witnessed in 

 the island, during nearly a month spent there in September 

 to October 1875 (in chapter xx. of his Siberia in Europe), 

 is most interesting ; and I refer to it here chiefly for the 

 sake of pointing out a very important error as to the cause 

 of a very singular fact recorded there by Herr Gatke, who 

 for fifty years observed and registered the migrations both 

 in spring and autumn with great accuracy, and formed a 

 collection of birds there, perhaps more extensive than could 

 be made at any other station in Europe. The fact ob- 

 served was, that, during the autumn migration, as regards 

 many of the most abundant species, the young birds of the 

 year, that is, those that had been hatched in the far north in 

 the preceding June or July, and who were, therefore, only 

 about three or four months old, arrived in Heligoland 

 earliest and alone, the parent birds appearing a week or two 

 later. This is the fact. It has been observed on Heligo- 

 land for half a century ; every resident on the island knows 

 it, and Mr. Seebohm declares that there can be no doubt 

 whatever about it. The inference from this fact (drawn by 

 Herr Gatke and all the Heligolanders, and apparently 

 accepted by almost all European ornithologists) is, that 

 these young birds start on their migration alone, and before 

 their parents, and this not rarely or accidentally, but every 

 year — and they believe also that this is a fact, one of the 

 most mysterious of the facts of migration. Neither Mr. 

 Seebohm nor Professor Lloyd Morgan (in his Habit and 

 Instinct) express any doubts about the inference any more 

 than about the fact. Yet the two things are totally distinct ; 

 and while I also admit the fact observed, I totally reject the 

 inference (assumed to be also a fact) as being absolutely 

 without any direct evidence supporting it. I do not think 

 any English observer has stated that the young of our 

 summer migrants all gather together in autumn and leave 

 the country before the old birds ; the American observers 

 state that their migrating birds do not do so ; while many 



