70 The Under-Water World 



hairs, and which serve for walking, 

 swimming, and in a few forms, for 

 breathing. The powers of regeneration 

 which these worms possess are very 

 remarkable. If cut in half the head 

 grows a new " tail-end/' and the hinder 

 portion a new head. Some, if split 

 longitudinally, still go marching on, the 

 lost side being grown again in a com- 

 paratively short time, material for the 

 purpose being taken from the original 

 side, the entire worm losing in length as 

 it gains in thickness. 



One of our best known members of 

 the group is the Sea Mouse (Aphrodite 

 aculeata), a stoutly-built creature covered 

 with prismatic bristles measuring nearly 

 half a foot in length. It is a favourite 

 item in the diet of many bottom-feeding 

 fish. Nearly allied is the common Rag 

 Worm (Nereis diver sicolor] , and the Her- 

 mit Crab Worm (Nereis fucata) that 

 foists itself upon the crustacean, sharing 



