Parasitic Copepoda of Fish. 9 



The literature being so scattered makes the investigation 

 difficult — all the more so as nearly every author has his own 

 scheme of classification. I propose now to use that drawn up 

 by Gerstaecker, which is founded more on the minute anatomy 

 of the animals, and is the most recent, though that used- by 

 Dr. Heller in his great work is very admirable. A large 

 number of the genera described by both these authors are, 

 however, purely tropical and do not come within the scope of 

 this paper. The most difficult to assign definite places to are 

 the very much differentiated members of the family Lernjeo- 

 podidge, where I believe the character of the male is the only 

 safe guide. I would specially point out that the distinction 

 given separating the genera Brachiella and Anchorella, viz. 

 the fusion of the second pair of maxillipeds partly or wholly, 

 is not a reliable one. It would be much better to found these 

 genera on the structure of the pigmy males, which are quite 

 distinctive ; but, unfortunately, these latter are not all known 

 or figured. 



From a collector's point of view one is quickly struck by 

 the much greater susceptibility of some fish over others and 

 the large number of parasites found on them individually. 

 For instance, it is rare to find a fairly grown cod {Gadus 

 morrhua) without being able to take many specimens of the 

 small semitranslucent Anchorella uncinata attached to the 

 folds about the lips and in the gill-cavity. In its mouth and 

 on the palate will be seen frequently half a dozen specimens 

 of Caligus curtus, on the gills, deeply imbedded, a Lemea 

 Iranchialis, and on the body sore places where numbers of 

 Caligus Mulleri have been fixed. Again, one is almost 

 certain in a hake (Ale^'lucctus vulgaris) on opening the mouth 

 to find one or more specimens of Chondracayithus merluccii 

 firmly fixed to the tongue, floor of the mouth, or palate, 

 generally surrounded by mucus. In one case I removed 

 thirty-three from the palate of a fish, leaving a raw ulcerated 

 surface behind. The hake has two other fixed parasites 

 attached to the gills — Brachiella insidiosa and Brachiella 

 merlucciiy — both fairly abundant. 



All the Gadida^ seem to be infested. 



The Gurnard family, too, are very prolific both in variety 

 and number of specimens ; but it is generally only in the well- 

 grown fish that the parasites are found, these being Caligus 

 rapax, Caligus diaphanus^ Brachiella impudica, and Bra- 

 chiella bispinosa. 



Tucked away in the anterior angle of the gills of Zeus 

 faber will almost certainly be found on either side one specimen 



