LIFE-UISTORY OF THE COMMON NEMATODE OF THE DOGFISH. 441) 



27. Some Observations on the Structure and Life-History 

 of the Common Nematode of the Dogfish (Sci/lliion 

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

 Lecturer and Demonstrator in Zoology at University 

 College, Cardiff. 



[lleceivcd May 15, 1920 : Uead November 2, 1920.] 

 (Text-tigures 1-3.) 



Introduction. 



In the following pages an account is given of the parasitic 

 Nematode, Proleptus scillicola, together with some observations 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 Plymoutii, 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 liere 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 connnon, 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 

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

 been reported from S. catidas (5), /S'. stellare (1), Raia claiKda (1), 

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

 examining one Scyllium catidus, and this specimen was absolutely 

 free from infection. 



Other species of the same genus under a different generic 

 name have been reported and briefly described as follows : — 

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

 stomach of Scyllinm iinriioratum ; Sjnrojyterina africana (6) 

 Linstow, from stomach of Anguilla sp. (?) ; Spiropterina elegans 

 (12) Orley, f rom the stomach of Hexacanthus griseus ; Sp)iro- 

 pterina dacnodes (4) Creplin, from the oesophagus of Rata clavata 

 and the stomach of Squalus mustelas. 



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

 attached within their hosts; when attached, it is always by tlie 

 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. 



