264 II. I.VNDHURST DUKE. 



few small water-snails are much appreciated. Owing' to tlie 

 transparent nature of the integument in Glossosiphonia, 

 the parasites are visible in the living leech ; and if the latter be 

 forcibly pressed between two slides provided with waxcornei's, 

 and examined under a low magnification, the gregarines may 

 sometimes be detected in the stomach diverticula and intes- 

 tine. Unfortunately, howevei-, this method of diagnosis is 

 by no means infallible, as the numerous pigment-cells with 

 their clear nuclei look very like gregarines, and render 

 accurate observation impossible. 'J'lie gregarines occur in 

 the hindermost stomach diverticula and the intestine, just as 

 indicated by Bolsius in his diagram. The cysts are found in 

 the same regions of the alimentary canal, but are especially 

 numerous in the intestine. 



Examination of sections shows that cysts can develop :is 

 far as the sporoblast stage in the intestinal canal of the host, 

 though they are often expelled with the fteces at a much 

 earlier stage in development. 



In sections just above the anus no cysts were to be seen. 

 This part of the gut was almost occluded by a mass of 

 cephalonts and some sporonts of a peculiarly blunt outline. 

 The leech from which these sections were cut had previously 

 evacuated fteces containing a few very early cysts among 

 a greater number in which sporoblasts could be distinguished. 

 As many as ten cysts have been counted in one section. 



To obtain the gregariue, the infected leeches were partially 

 dried on blotting-paper and the under-surface opened by 

 three incisions — two parallel and close to the margins, and 

 one at right angles to the long axis of the animal, at about 

 the junction of the middle and anterior thirds. The flap of 

 tissue was then carefully turned backwards towards the anal 

 sucker, the animal being placed in a watch-glass containing 

 normal saline solution. The gut-contents were thus emptied 

 into the saline, together with connective tissue, which is of 

 no account. By the aid of a hand-lens the gregarines could 

 now be seen sticking to the bottom of the glass, or still fixed 

 to fragments of the host-tissue. These latter are useful in 



