128 Instinct and its Lessons 



and Diodorus. To this, when it was land, the 

 Lemmings, according to Mr. Crotch, acquired the 

 habit of migrating, and the habit has persisted though 

 the land has sunk fathoms deep in the ocean. To 

 this theory, which is adopted likewise by a writer 

 in the Encyclopedia Britannica> there is the obvious 

 objection that the Lemmings, which do not migrate, 

 alone perpetuate the race, and must therefore be 

 supposed to hand on the instinct, which in their own 

 persons they do not exhibit. Is it not more truly 

 scientific to acknowledge that we know nothing at 

 all of the matter, and cannot even conceive a satis- 

 factory hypothesis? This suicidal instinct is no 

 doubt mightily convenient to the world at large, in so 

 effectually checking the unlimited increase of these 

 prolific rodents, but within the limits of their race it 

 cannot be said to have any advantages to recommend 

 it for Natural Selection. 



But we need not weigh these improbabilities, how- 

 ever grave they be, in discussing the question as 

 to whether the knowledge required for migration be 

 acquired by education or implanted as instinct, for, 

 as a matter of fact, the young birds of the year, 

 in the case of the great majority of species, migrate 

 before the old ones, and perform their first journey 

 with no guide but that which they can themselves 

 supply. As if to leave no doubt upon the subject, 

 there is one notable exception. The Cuckoo, reared, 

 in almost every case, in a non-migrant's nest, 1 having 

 no converse with its own parents, leaves the country 

 a month after they have gone, and when every 

 possibility of a personally-conducted voyage has van- 

 ished. 



Still more hopeless would be his task who should 

 maintain that in the case of fish, "the voiceless children 

 of the incorruptible," instruction of any sort is imparted 

 by the older to the younger generation. Salmon are of 



1 Far most commonly in that of the Meadow-pipit, and after 

 that of the Hedge-sparrow, or Wagtail. 



