312 RAMBLES OF A NATURALIST. 



furrows dry and harden in the heat of the sun. 

 At such times the aeon cannot be used, and to en- 

 able these boats to be worked easily, it would be ne- 

 cessary to level every part of this vast basin, which 

 extends over a space of more than 75,000,000 of 

 square yards. Such a labour as this, if human in- 

 dustry were to attempt it, would obviously be found 

 to be impracticable, even if the whole population of 

 the district were to devote the entire summer to the 

 task. Yet this herculean labour is accomplished in 

 less than a month through the agency of a Crusta- 

 cean, whose body, which is scarcely thicker than a 

 piece of sewing cotton, is not more than half an inch 

 in length including the antenna?. 



Towards the end of April the little Crustaceans, 

 termed by the fishermen the Pernis ( Corophium longi- 

 curne), arrive from the open sea in myriads. Guided 

 by their instinct, they come to wage an exterminating 

 war against the Annelids, which during the whole 

 winter and early spring have multiplied undisturbed. 

 As the tide rises, these voracious hordes are seen 

 moving about in all directions beating the mud with 

 their long antennas, and pursuing Nereides and the 

 Arenicolse to their deepest recesses. When once 

 they discover one of these animals, which are several 

 hundred times larger than themselves, they combine 

 to attack and devour it, and then resume their eager 

 chase. This carnage never ceases till the Annelids 

 have almost entirely disappeared, but by that time 

 the entire bay has been dug up and levelled, and the 

 aeons are again able to move readily over its surface. 

 Before the close of May the work is completed, and 



