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Part III. — Eighteenth Annual Report 



(2) Isopoda Parasita. 



Several species of the parasitic Isopods of fishes have been observed, 

 of which the following may be referred to : — 



Gnathia maxittaris (Mont.). 



Specimens of Gnathia, which I consider to belong to this species, have 

 been found adhering to the gills of the common gurnard, Trigla gurnardus, 

 and of the lemon sole, Pleuronectes microcephalics, sent by the " Garland " 

 from the Clyde to the Laboratory at Bay of Nigg. Females only of the 

 Gnathia were observed, and in each case the Isopod was attached to the 

 gills, under the gill-covers. 



JEga stromii, Liitken. 



A specimen of this Isopod was presented to me by one of the men on 

 board a beam-trawl fishing boat belonging to Granton. The crustacean 

 was found adhering to a large cod captured in the North Sea a consider- 

 able distance south-eastward of May Island. 



u'Ega triolens, Leach. 



A specimen of this species was brought to me by a Rothesay fisherman, 

 who obtained it on a cod he had captured on his fishing lines in Rothesay 

 Bay. One was obtained on a torsk in Aberdeen Fish Market on 15th 

 September 1899. 



JEga monophthalma (Johnston). 



A fine specimen from a large cod captured by one of the Shetland 

 fishing boats was handed to me for examination ; it undoubtedly 

 belonged to the species named, as described and figured in Prof. G. 

 0. Sars' Crustacea of Norway, vol. ii. 



I have had an opportunity of examining another fine species of yEga, 

 viz., JEga psora. The species is included in the British fauna, but the 

 specimens I saw were obtained on cod captured in Icelandic waters. 



Cirotana borealis, Lilljeborg. 



This Isopod is not very rare in the deeper parts of the Clyde, as, for 

 example, to the east of Arrau, in Kilbrennan Sound, and Loch Fyne, but 

 I have never happened to find it there as a parasite. It has, however, 

 been found adhering to several of the fishes brought to the Fish Market 

 at Aberdeen, and on one or two occasions it was observed to be 

 moderately frequent. I have notes of its occurrence on the following 

 fishes : — The grey skate, Rata batis ; the saithe, Gadus virens ; the torsk, 

 Brosmius brosme ; and the conger, Conger vulgaris. The Cirolana were 

 observed on the saithe in June, and on the conger in October, and on the 

 other two species of fishes during the intervening months. 



(3) Amphipoda Parasita. 



There are only two Amphipods to which I wish to refer, viz. : — 



Callisoma crenata, S pence Bate. 



So far as I have been able to study the habits of this Amphipod, it 

 seems to be a species whose energies are devoted for the most part to the 

 removal of dead and decaying animal matter, rather than the destruction 

 of living tissue. It would seem, however, that it does not confine its 



