156 VITALISM AND SCHOLASTICISM 



passing a very early existence, the details of 

 which are unknown to us, each rises to the 

 surface as a transparent, knife-like, large-eyed 

 creature known as Leptocephalus. In this 

 stage it swims about and apparently never 

 feeds, and becomes gradually transformed into 

 the glass-eel, a creature shaped like a knitting- 

 needle and about three and a half inches long. 

 After a year it passes up with some millions 

 of other elvers into the fresh waters of some 

 river, and there as we all know it abides as 

 the familiar eel for some years. If it does not 

 succumb to the night-line or any other device 

 of its foes, after a few years it sets out once 

 more for the sea, becoming silver-coated and 

 large-eyed on its way. Its journey is for breed- 

 ing purposes. It travels enormous distances, 

 for the eels from the Baltic rivers have, it is 

 said, three thousand miles to traverse. Why ? 

 Because the Baltic waters are too cold and 

 those of the North Sea too shallow for its 

 purpose. Arrived at the spot of its desire it 

 is assumed that breeding takes place, but one 

 thing seems pretty sure, namely, that the eel 

 never returns. How can this be explained on 

 mechanical lines ? It is difficult to see. Bio- 

 logists tell us that the eel is really a deep-sea 

 fish which has taken to colonizing fresh or 

 brackish waters just as the salmon is a fresh- 



