LIFE-lilSTOIlY OF THE COMMUX NEMATODE OF THE JUoUFISU. 449 



27. Some Observations on the Structure and Li£e-History 

 of the Common Nematode of the Dogfish {Sci/Uium 

 cankula). By J. H. Lloyd, M.Sc, F.Z.S., Assistant 

 Lecturer and Demonstrator in Zoology at University 

 College, Cardiff. 



[Received May 15, 1920 : Read November 2, 1920.] 

 (Text-figures 1-3.) 



IntrodiLclion. 



In the following pages an account is given of the parasitic 

 Nematode, Proleptus scillicola, together with some ohservations on 

 its life-history. The work was carried out, partly in the Zoolo- 

 gical Department of the University of Birmingham and partly 

 at the Marine Biological Laboratory at Plymoutli, towards the 

 end of 1914 and the beginning of 1915, but until now I have 

 been uuable to write up my results for publication, owing to my 

 absence on military service. 



I should like here to express my gratitude to Professor F. W. 

 Gamble for his kindly criticism and advice during the course of 

 this work. My thanks are also due to the Board of Studies in 

 Zoology of the University of London for the use of their table 

 at Plymouth, and to the Royal Society for providing a grant 

 which enabled me to procure the necessary material. 



A description has been thought desirable because, although 

 the worm is exceedingly common, no complete account of its 

 anatomy exists, and its life -history has never been worked out. 



Proleptus scillicola occurs in the alimentary canal of Scyllium 

 cauicida from the mouth to the pyloric constriction. It has also 

 been reported from ,S, catulus (5), S. stellare (1), Eaia clccvafa (1), 

 and Paia circidaris (1). I have only had the opportunity of 

 examining one Scyllium catulus, and this specimen was absolutely 

 free from infection. 



Other species of the same genus under a difi"erent generic 

 name have been reported and briefly described as follows : — 

 Spiropterina inflata (8) Linstow, attached to the wall of the 

 stomach of Scylliiion iinmoraluin ; Spiropiei'ina africana (6) 

 Linstow, from stomach of Angidlla sp. (?) ; Sjnrojiterina elegans 

 (12) Orle}^, from the stomach of Hexacanthus griseus ; Sjnro- 

 pierina dacnodes (4) Creplin, from the oesophagus of Raia clavata 

 and the stomach of Squalus musteliis. 



The worms are white in colour, and occur either free or 

 attached within their hosts ; when attached, it is ahvays by the 

 tail-end. 



The females are considerably larger than the males, from which 

 they are easily distinguished by the tail, which in the male is 

 coiled. 



