SWIMMING ANIMALS 85 



their eggs or their very tiny young. Izaal- Walton in his 

 Compleat Angler says : " Some say that they breed, as 

 worms do of mud ; as rats and mice, and many other living 

 creatures are bred in Egypt, by the sun's heat when it 

 shines upon the overflowing of the river Nilus ; or out of 

 the putrefaction of the earth, and divers other ways . . . " 

 " and others say, that as pearls are made of glutinous 

 dewdrops, which are condensed by the sun's heat in those 

 countries, so eels are bred of a particular dew, falling in the 

 months of May or June on the banks of some particular 

 ponds or rivers . . . which in a few days are, by the sun's 

 heat, turned into eels." 



But just as we know that pearls are not made from dew- 

 drops, so are we now certain that eels do not spring from 

 mud, or putrefaction, or drops of dew. For in the year 

 1922 a great Danish oceanographer, Dr. J. Schmidt, found 

 the true spawning place of the eel and cleared up the 

 mystery once and for all. He disclosed the amazing fact 

 that when the eels in our rivers become mature they set 

 off on one of the longest journeys as yet known to be under- 

 taken by any fish. 



When the common fresh-water eel of our rivers has 

 reached a length of about a foot, it changes its appearance 

 and puts on what is known as its " spawning livery." 

 Instead of its usual yellow colour it becomes quite silvery 

 in appearance and hence at this stage is known as the 

 " silver eel." In this condition the eels work their way 

 down to the mouths of the rivers. In the late summer and 

 autumn this migration takes place and the eels push on 

 out of the estuaries and into the open sea. Then starts 

 the long, long journey out into the deep water and so into 

 the Atlantic Ocean. Of the speed at which' the silver eels 

 go on their journey we know little. Once into the deep 

 water they become lost to our observation. In the Baltic 



