Instinct and its Lessons 125 



What prompts them to start on such an enterprise? 

 and what teaches them to know how to set about it? 

 Yet this is not all the wonder. Recent observation 

 has established the fact that the routes followed in 

 migration are well defined, the sea voyage being by 

 no means reduced to a minimum. 1 Whence comes 

 the knowledge which makes it possible to steer such a 

 course ? 2 



It has been attempted to maintain that here too, as 

 well as in music and architecture, the experience of the 

 old is communicated to the young, and that it is a 

 matter, accordingly, not of instinct, but of education. 

 The teachings of observation, however, are all the other 

 way. In the first place, to say that any bird, old or 



1 We are told that these routes follow the lines of least depth 

 of water, and it is inferred, that the birds having grown accus- 

 tomed to these lines, while they were dry land, have been unable 

 to forget them ever since. Of course, if the fact be correctly 

 established it must be accepted ; but otherwise grave and obvious 

 objections present themselves. In flying over land, the birds, 

 I believe, follow the river basins, the valleys, not the hills. The 

 track of what once were hills, the shallower waters, cannot there- 

 fore be the oldest memory of the race. If that older memory has 

 been supplanted by a newer why not that again by a third? It 

 would seem that it should have been so most emphatically on 

 principles of Natural Selection. Enormous numbers of birds perish 

 in the sea passage. Tens of thousands, we are told by Dr. Robert 

 Brown, are drowned yearly. Here is a case where Natural Selec- 

 tion should work at high pressure. Birds accidentally taking a 

 shorter route should have been so favoured in the struggle for 

 existence as, by this time, to have produced a race following a 

 mathematical straight line betwixt the nearest points, from shore 

 to shore. 



2 An extraordinary explanation has been imagined by an observer 

 quoted by Mr. Romanes. He is of opinion that birds always starl 

 their migration when the wind is from the south, and that the 

 instinct is fully accounted for by the pleasurable sensation they 

 experience in flying against the warm breeze. This appears to be 

 an excellent example of the theoretical manufacture of facts. On 

 the Qth of October, when the Martins before mentioned took their 

 departure, the wind was all day N.N.E., except for a short period 

 when it got round to N.N.W., as shown by its self- registration in 

 our Observatory. 



