of the Fishery Board for Scotland. 



145 



conditions. Their structure has, because of their parasitic habit*, become 

 more or less altered, and, in consequence of this, the forms which not a 

 few of them have assumed are greatly at variance with those which 

 usually characterise free-living species. Some of these parasitic crustaceans 

 have assumed forms so strangely abnormal and grotesque that even the 

 most experienced naturalists have failed to recognise their relationship to 

 the Crustacea, and only by the study of their development and life-history 

 have their true affinities been determined. 



Amongst crustacean parasites of fishes, the Copepoda is the group that 

 is probably the most largely represented, and I therefore propose to 

 devote the chief portion of this paper to the consideration of this group; 

 a few of the Isopoda and Amphipoda that have been observed are also 

 referred to. 



A small list of Copepod-parasites of fishes w T as published in Part III. 

 of the Twelfth Annual Report of the Fishery Board for Scotland (1894). 

 Since that time other species, besides those enumerated in that list, have 

 been obtained, and during the past summer special attention has been 

 devoted to the study of these organisms, with the result that several 

 interesting forms have now to be added to the copepod fauna of Scotland. 



The crustacean parasites mentioned in the sequel have for the most 

 part been obtained on lishes captured in the Firth of Forth, in the Firth 

 of Clyde, or in some other part of the sea around the Scottish coasts ; a 

 few interesting species have been obtained on fishes brought to the Fish 

 Market at Aberdeen, and with regard to these I am unable to state the 

 place where the fishes were captured, though I believe that those on 

 which the parasites were found were in most instances taken somewhere 

 off the coast of Scotland. 



In the preparation of these notes various works on parasitic Copepoda 

 have been consulted, and in this respect the late Dr Baird's History of 

 the British Entomostraca is still indispensable. Several valuable papers 

 on the copepod parasites of fishes have in recent years been published by 

 Dr. Basset-Smith, R.IsT., one of the latest being A Systematic Descrip- 

 tion of Parasitic Copepoda found on Fishes, with an enumeration of the 

 known species. * 



The classification of Gerstackerf is that which Dr. Basset-Smith has 

 chiefly followed in his Systematic JJesrription, and as it appears to be the 

 one which is now generally adopted, the species mentioned in the present 

 paper are arranged as far as possible in conformity with it. 



Mr. Andrew Scott, assisted by Mrs. Scott, has prepared the drawings 

 necessary for the elucidation of the species recorded here. 



I have also to acknowledge my indebtedness to Mr. Peter Jamieson, 

 the Laboratory Assistant, for help in the collection of specimens for this 

 paper. 



The COPEPOD Parasites of Fishes. 



According to recent classification the Copepod parasites of fishes have 

 been arranged under seven families, the names and arrangement of which 

 are as follows : — Ergasilidse, Oaligidye, Dichelestidee, Philichthyidae, 

 Lermeidae, Chondracanthidai, and Lerna3opodid&>. The Philichthyidae is 

 the only one of the seven families which does not seem to be represented 

 in the British fauna ; but even this family may also yet be found to have 

 representatives amongst the Copepod fauna of our seas. 



* Prqc. Zool. Hoc. London, April 1899. 



f Vide Copepoda in Bromi's " Klassen uud Ordnungen des Thierrcichs," v. i, 

 (1866-74). 



