Life-history of the Eel 87 



§9. The Living Past. 



The drowsy dog turns round and round, making 

 itself comfortable in the imaginary herbage of the 

 hearth-rug. What its wild ancestors — whether 

 they were wolves or jackals — did ten thousand years 

 ago, or more, it is doing to-night. The past is living 

 still. And the horse that shies at a sudden movement 

 in the hedgerow sees the snake that bit its ancestor's 

 heel! Cows transported from very conventional con- 

 ditions in Scotland to the wilder environment of a 

 ranch in California have been known to hide their 

 calves in a thicket while they grazed in the open — a 

 sudden return to a habit older than domestication. 

 In many different ways the past lives on in the 

 present. Let us take an instance where this idea 

 illumines a life-history. 



Everyone knows that the Common Eel has a very 

 remarkable history. Its life begins far out in the 

 Atlantic, where the knife-blade-like transparent 

 larvae swim and drift in the open waters. The Ameri- 

 can species goes westwards, the European eastwards, 

 for their birthplaces overlap, perhaps recalling a 

 time when the continents were nearer one another 

 than now. When the European forms are in their 

 third year they are approaching the coasts and they 

 change into cylindrical elvers, the length of our first 

 finger and the thickness of a stout knitting needle. 

 They ascend the rivers in the well-known "eel-fare" ; 

 they reach the slow-flowing stretches and the ponds. 

 In the course of from four to seven years they have 



