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THE WORM-LIKE ANIMALS 



naceous rim. The head is surrounded by a circlet of small feelers. This worm 

 one of the smallest of its group lives as an external parasite upon annelids, 

 especially upon tube-making forms, such as Clymene. 



The worms which constitute a second section of the present suborder differ 

 from the foregoing in possessing several sucking discs at the hinder end of the 

 body. Among them is a curious creature well deserving its name of Diplozoum 

 paradoxum, since it consists of two complete, mature similar halves, each possess- 

 ing every attribute of a perfect animal (a). Each of the pointed front ends has a 



LIFE HISTORY OF DOUBLE WORM (magnified). 



mouth aperture, and close to it a couple of small sucking discs; while each individ- 

 ual has a separate intestine consisting of a median tube and innumerable side 

 branches. At the hinder end of the body are two suckers sunk in a depression, 

 and protected by four hard buckle-shaped organs. The double worm lives on the 

 gills of several species of fresh- water fish, the gudgeon and minnow for instance. 

 The eggs are elongate and provided at one end with a fine thread-like appendage 

 (). In this egg the young (<:) which at the time of hatching is only about one 

 hundredth of an inch takes about a fortnight to develop. It is covered with 



