320 CKESSWELL SHEAliER. 



jaws. Its fibres form an oval mass attached directly to the 

 jaw blades. Into this mass some of the striated muscle-fibres 

 are inserted. Its action is hard to understand. It is well 

 shown in Foettinger's figures. In the movements of the 

 jaws the lower blades are sometimes seen to separate con- 

 siderably from one another posteriorly, and it is possible this 

 motion is brought about by them. What this movement has 

 to do with the teeth I have been unable to observe. Tliis 

 muscular organ appears to be wanting in Stratiodrilus, as 

 it is not shown in Haswell's figures. 



On either side of the jaws about their middle there pro- 

 trudes laterally a small pear-shaped gland composed of from 

 three to four large granular cells with conspicuous nuclei 

 (text-figs. 1 and 2). This gland opens into the mouth or the 

 anterior part of the oesophagus, and is evidently of a mucous 

 nature, as it absorbs the methyl-blue colour very strongly 

 when the parasites are placed in it for a short time. The 

 protoplasm of the gland-cells is finely granulai*, each having 

 a very large, darkly staining nucleus with a prominent 

 nucleolus. The duct of the gland converges and opens on 

 the ventral side of the mouth. The posterior portion of the 

 organ lies against the muscular pad of the ends of the lower 

 jaws, while its dorsal surface touches the cuticle of the dorsal 

 surface of the head. 



In position and structure it is in all respects similar to the 

 glands occupying the same position in Dinophilus, and 

 undoubtedly answers the same purpose. In Protodrilus, 

 also, similar glands are present. It appears to have been 

 overlooked by Foettinger. In fig. 1 of his paper he shows a 

 mass of tissue on either side of the jaws, which in great part 

 belongs to these salivary glands, and not to the jaw muscles, 

 as he evidently thought. Haswell makes no mention of its 

 presence in Stratiodrilus, although it is probably present 

 here also, for he shows a number of round cells in the position 

 that it occupies in Histriobdella. 



