WHIRLPOOLS 



they have survived. They remain for three years near the 

 mouths of the rivers, swelhng and growing in length all 

 the time. Then, while their thyroid glands are develop- 

 ing, they move farther and farther up the rivers, until 

 they have attained a length of as much as three feet, 

 and a weight up to thirteen pounds. 



During their progress up the rivers there has been no 

 differentiation in sex — they have been sexually un- 

 developed throughout the journey. At last — seven or 

 eight years have elapsed since they left the Sargasso — 

 they become distinct sexes. 



They are now far up the rivers, and the males have 

 become sexually mature, but (unlike salmon) the eels do 

 not have their young there at journey's end. Why have 

 they come so far — struggling through the waters of the 

 ocean, resting awhile in the estuaries, and battling 

 against the river's seaward currents to these places? As 

 these are not their breeding grounds the driving impulse 

 cannot be sexual. 



But now — first to the males — comes the home-hunger 

 which takes them all the long journey back again. FeeHng 

 the compelling force of the Sargasso call, the mature 

 male eels leave their fresh-water homes high up in the 

 rivers and swim back until they reach salt water again, 

 plunging into it in their shining myriads and battling 

 their way unerringly outward — farther and farther out- 

 ward — through the ocean wastes until they reach their 

 objective. There is no explanation of this apparently 

 senseless separation of the males from the females at the 

 very climax of their sexual development. For the females 

 wait, back there up the rivers, not weeks or months but 

 years, before following the males. They are between ten 

 and fifteen years old before the Sargasso call comes to 

 them. When the moment arrives they, too, go down the 

 rivers, through the estuaries and out to the open sea — 

 anything up to eight years later than the males who have 

 preceded them. 



107 



