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S. J. JOHNSTON. 



in front of the excretory vesicle. The two limbs are pro- 

 vided on each side with short diverticula. 



Excretory system. — The form of the excretory system 

 is peculiar and highly characteristic. A short V-shaped 

 vesicle, opening by the excretory pore at the posterior 

 end, gives off on each side a very large collecting vessel, 

 which runs forwards, about halfway between the intestinal 

 limbs and the sides of the body, right up into the region of 

 the oral field. Bach of these collecting vessels is joined 

 on either side by vessels which form anastomosing loops, 

 that cover the whole dorsal surface of the body. In 

 Clinostomum marginatum this part of the excretory system 

 (Osborn, figs. 3 and 4) lies ventral to the intestinal limbs, 

 but in my form they are undoubtedly dorsal. These anas- 

 tomosing loops communicate with a very extensive system 

 of sub-cuticular spaces and channels, as they do also in 

 C. marginatum. I have not been able to trace the fine 

 recurrent vessel described by Osborn in 0. marginatum, 

 but cannot say definitely that it is not present, as I have 

 only one series of horizontal (parallel to the ventral sur- 

 face) sections, and in such a series its connection with 

 the collecting tubules would be particularly difficult to 

 demonstrate. 



Nervous system. — A pair of large cerebral ganglia lie 

 one on each side of the oesophagus, on the dorsal side of 

 which the transverse connecting commissure passes. 

 Besides the thick nerve cords which run back to the pos- 

 terior end almost in a line with and ventral to the main 

 collecting vessels of the excretory system, a number of 

 pairs of small nerves are given off by the cerebral ganglia 

 to neighbouring parts. 



Genital system. — The gonads lie in the posterior third 

 of the body, the anterior testis projecting a little into the 

 middle third. The testes are roughly triangular, with deep 



