FLAT - WORMS. 
465 
organ is supported by a set of radiating spines, eight in number, and has a soft 
membranaceous 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 
life-history of double-worm (magnified). 
paracloxum, since it consists of two complete, mature similar halves, each possessing 
every attribute of a perfect animal (a). Each of the pointed front ends has a mouth 
aperture, and close to it a couple of small sucking-discs; while each individual 
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 (6). In this 
egg the young ( c )—which at the time of hatching is only about one hundredth of 
an inch—takes about a fortnight to develop. It is covered with cilia, has two 
vol. vi. —30 
