BY S. J. JOHNSTON. 735 



longitudinal vessels, given off from the stem of the vesicle, end in 

 front in an anastomosing network of vessels, which is connected, 

 by a fairly large opening (Fig. 10) on each side, with a large smus 

 surrounding the oral sucker. A similar sinus also surrounds the 

 ventral sucker. Similar sinuses surrounding the suckers have been 

 found by Braun(2, 5) in Mesaulus grandis R., and in Echinostoma 

 incrassatum, Dies., but their connection with the excretory system 

 was not observed (5, p. 27). All these vessels, including the net- 

 work and the sinuses, are lined in the same way by a nucleated 

 syncytium. Given off from them are smaller intracellular tubes 

 that end in flame-cells. The latter are more numerous at the 

 anterior end of the body. 



Opening into the sinus that surrounds the oral sucker, I find a 

 pair of tubes of quite different character. The walls are thicker, 

 and elongated patches of cilia (Fig. 9) project into the lumen. The 

 intervals between these groups of cilia are small, so that the tube 

 is ciliated in the greater part of its length. These two tubes run 

 backwards, one on each side, to a level some distance behind the 

 testes, where each jDasses into a tube lined by columnar nucleated 

 cells, but bearing no cilia. These latter tubes, which I have marked 

 "supplementary tubes" in Fig. 9, run forwards, parallel to their 

 ciliated companions, and backwards to the posterior end of the 

 body where they bend round, and are continued forwards again for 

 some distance. At about the level where they disappear, a second 

 forwardly running branch is given off from the parent supplemen- 

 tary tube, and this second branch reaches a level somewhat in 

 front of the junction of the supplementary tube with the ciliated 

 tube. The supplementary tube and its branches gradually become 

 smaller and thinner-walled, and finally end in a system of inter- 

 cellular spaces lying in the parenchyma. The function of all these 

 tubes and sinuses is, no doubt, respiratory as well as excretory, and 

 the fluid in their cavities is kept in circulation by the ciliated 

 tubes. 



The genital pore is situated on the ventral surface, near the 

 middle line, just in front of the ventral sucker. The gonads lie 

 close together, occupying about the middle third of the body- 



