20 Dr. W. Nlcoll on tie 



preservation, which may account for the fact tliat no previous 

 mention has been made of tliem. In the living animal, 

 however, they present one of the most striking features. 



The average length of my specimens collected at St. 

 Andrews is 1"4 mm. The ventral sucker is situated at a 

 distance of about g of the body-length from the anterior end. 

 The diameter of the oral sucker is ^^ of the body-lengtli and 

 that of the ventral sucker rather more than \. The sucker- 

 ratio is therefore approximately 2 : 3. Miss Lebour makes 

 it 1 : 2, but in her drawing it is almost exactly 2 : 3. Tlie 

 diameter of the pharynx is usually -^q of the body-length. 

 The average size of the ova is '021 x '0145 mm. 



Ilemiurus communis, Odhner. 



In addition to the hosts already recorded for this species 

 must be mentioned Trigla gurnardus, Cothis scorphis, and 

 Gadus callarias. It was also erroneously recorded in Part I. 

 as Ilemhirus appendicvlatus (Rud.) from Cottus hubalis, 

 Centronotus guernellus, Ilijipoglossus vulgaris, and Anguilla 

 vulgaris. This makes tiie number of British hosts twelve *, 

 but there are at least another nine fishes in which I have 

 found it. It thus rivals Derogenes varicus as the most widely 

 distributed Trematode parasite of marine fishes. This is 

 probably due to the fact that the larval stage of both is 

 passed in some very common Crustaceans, most likely 

 Copepods, Levinsen's discovery of the larva of Derogenes 

 varicus in the Polychget worm, Harmotho'e imbricata, has never 

 been confirmed, so that much doubt must remain as to the 

 correctness of liis observation. Pratt's discovery of true 

 Hemiurid larvee in Copepods indicates that they are really 

 the hosts in which to look for the early stages of Ilemiurus 

 forms. 



A word may not be out of place here in reference to the 

 recent proposal by Looss f to apply the terms soma and 

 abdomen respectively to the body and appendicular part of 

 appendiculate Distomes. The word abdomen has, apart from 

 its classical meaning, a recognized and definite significance 

 in the anatomical terminology not only of Vertebrata but 

 also of Invertebrata, and it seems unreasonable to apply such 

 a general and well-known term to a single, small, specialised 

 part. Such a use of the term has no justification on ana- 

 tomical grounds, for in only a certain proportion of cases does 



* It is recorded by Johnstone as Distomwn appendictilatum from the 

 plaice, dab, and whiting. 

 t Zoul. Anzeig. xxxi. (1907) p. 585. 



