144 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



of the ventral sucker they are present only beneath the 

 rlorsal body wall. In the region of the testes they are 

 lateral (fig. 4) and do not appeal' on dorsal and ventral 

 surfaces. Behind the testes they are distributed round 

 the entire periphery of the body. They are very 

 numerous, and when the worm is contracted greatly 

 appear very closely packed together, so that it is almost 

 impossible to make ont the other organs. Indeed it is 

 only by killing the trematode in fresh water, and then by 

 flattening it out between two microscope slides during 

 fixation, that the animal can be preserved in a condition 

 fit for staining and clearing. 



Testis Excretory duct 



Fig. 4. Allocreadium labracis (Duj.). Transverse section through 

 posterior testis. 



The vitelline ducts have the usual disposition. It 

 is not difficult to trace most of their ramifications in a 

 successful preparation. One main longitudinal duct runs 

 along either side of the body, and to this numerous 

 ductules proceed from the follicles of the gland. At about 

 the transverse level of the ovary fairly wide transverse 

 ducts appear, and these run across towards the middle 

 line, uniting to form a rather large vesicle, which is, of 

 course, only an enlargement of the united ducts. From 

 this vesicle a slender efferent duct takes origin, and runs 



