126 Instinct and its Lessons 



young, has the minute geographical memory which 

 would be required to steer by between Lancashire and 

 Morocco, seems no more in accordance with what we 

 know of them, than to say that worms have a sense of 

 humour. What possible co-ordinates would serve them 

 out of sight of land, over the tracts of the unfruitful sea ? 

 Migration, moreover, is performed more by night than 

 by day, and to judge by the mad way in which the birds 

 then dash up against lighthouses, it would seem as 

 though they were hurried irresistibly on with far less 

 power of self-control than they ordinarily exhibit; as 

 young Salmon confined in a pond will throw themselves 

 on the bank when the season for going to the sea arrives. 

 For it must be remembered that birds are not the only 

 migrants : the wanderings of the Herring and the Salmon 

 are still more extraordinary, and of them it is a still less 

 hopeful task to attempt any explanation. What guiding 

 lines can be found in the waste of waters, even if it be 

 true, as has gravely been asserted, that Salmon-smolts go 

 down their native river tail first in order to observe what 

 should be their way up again ? 



Turtles, also, which at other times spread them- 

 selves far abroad in the ocean, manage to hit off 

 at the breeding season the little island of Ascension, 

 a tiny speck in the midst of boundless waters, which 

 many mariners with the aid of chart and sextant 

 have not been able to find. 



But the most extraordinary and inexplicable of all 

 migratory instincts, is afforded by a quadruped, the 

 Lemming. This little animal, a member of the 

 Mouse family and a close relative of the Water-rat, 

 lives habitually in the east of Norway, but at irregular 

 periods, varying from three years to ten, a large 

 portion of them set forth on the most mysterious 

 of pilgrimages. Their course is directed due west, 

 and thus does not lead them to the regions where 

 more plentiful food might be obtained, in the south. 

 They spend more than a year moving resolutely on, 

 turning neither to the right nor to the left for any 



