Internal Parasites of the Tweed Salmon. 119 



of Di'ummond with T. megacephalus, which is distinctly 

 separated from T. grossas by its tapering proboscides. In 

 the dead form tlie proboscides are rarely altogether retracted, 

 and they still resemble those oi .T. grossus. 



Tetrarhyyichus macrohoihrmSy Rud. Synops. pp. 131 & 453. 



Length 3-8 mm. Specimens occurred free in the body- 

 cavity, oftenest in the region of the liver and also encysted 

 on the outer wall of the oesophagus. When liberated from 

 cysts they were yellow, almost orange-coloured. Those in 

 the body-cavity were creamy white. T. megahothrius, E,ud,, 

 and T. apj^endiculatus, Rud., may be the same as the species 

 in question. 



The larva of Tetrahothrium minimum occurred in the mucus 

 of the pyloric cjBca. 



Tetrahothrium sp. 



A few larval forms were found in fluid in the rectum — 

 probably more advanced forms of the last species. 



Tcenia sp. 



One larva was observed. 



The list of parasites of the Tay salmon given by Prof. 

 M'Intosh* corresponds to the above in its thoroughly 

 marine character. 



Gatty Marine Laboratory, St. Andrews, 

 March 31, 1905. 



EXPLANATION OF PLATE V. 



Fit/. 1. Tetrarhynchus grossus, Rud. Length 30 mm. 

 Fig. 2. Ditto. Length 38 mm. 

 Fig. 3. Ditto. Length 29 mm. 

 Fig. 4. Ditto. Length 24 mm. 

 Fig. 5. Ditto. Length 30 mm. 



All from spirit-specimens. 



* Journ. Proc. Linn. Soc. vol. vii. pp. 145-154, 2 woodcuts. 



