450 MR. J. II. LLUYU OX THE STRUCTUUIS AND LIFE- HISTORY 



Historical , 



Some confusion appears to exist as to the correct generic name 

 of the Common Nematode of l^cyllhmi canicula. The first genei'ic 

 name iissigned was Prolejjiics by Dujardin (5) in 184r». lie 

 distinguished two species — Prolejitus acutus and Frolej)tus obiusas, 

 but as lie gives neither description nor diagram of Proleptas 

 ohtusus, it may be considered invalid. 



In 1860, Molin (11) described a nematode under the name of 

 llisiioce'jihalus dacuodes, which should apparently be refeired to 

 the genus Proleptus, as it difiers considerably from the remaining 

 species of 11 istiocephalus and ap^jears to be wrongly placed. 

 During the following year (1861) Van Beneden (2) described the 

 worm under the generic name of S'piropterma. 



Previous to Van Beneden placing it in a separate genus, it 

 was pi'ovisionally assigned by Greplin (4) to the genus Spirojiiera, 

 chiefly because its head-end bore some slight resemblance to the 

 Spiropteras of Taljm, Erinaceus^ etc. 



In 1870, Van Beneden (1) mentioned the worm under the 

 generic name of Corouilla, and distinguished three new species : — 

 Coronilla sciUicola, (Joronilla robasta, and Coronilla minata. 

 Neither the new genus nor the new sjoecies were descilbed, but 

 six drawings were given, which referred indiscriminately to two 

 of the species — viz., Coronilla robusta and Coronilla sciUicola. 



SpirojMrina appears to be the generic name by uhich the 

 worm is most commonly known, but Linstow (7) has put forward 

 a strong argument in favour of the name Prolepdus on the ground 

 of prioritv. For this reason I shall use the generic name I'ro- 

 leptus, but as Dujardin's species acutus evidently refers to a 

 distinct species which occurs in Scylliam caiulus, and his species 

 obtasus is difficult to determine, I propose to retain Van 

 Beneden's specific name sciUicola, and shall describe the worm 

 under the name of Prolepttus sciUicola. 



In addition to the foregoing, it has been briefly described by 

 Linstow (9). My observations differ from those of Linstow in 

 several respects, and his diagrams are inaccurate. 



Morphology. 

 (a) External Characters. 



The body is surrounded by a ver}^ thick, transparent cuticle, 

 which is finely ringed transvei'sely. Proleptus sciUicola possesses 

 extraordinary vitality. I have kept specimens alive in normal 

 salt solution for over 17 weeks, whilst Linstow (9) records the 

 fact that "specimens which had been in Miiller's fluid for 

 48 hours arrived in a living condition." 



The best results for whole mounts were obtained with Looss's 

 fixative. Worms killed in this manner are straightened consider-' 

 ably and retain their transparency. Perenyi's fluid proved to be 

 the best fixative for animals which were to be sectioned, whilst 

 Pa,ra-carmine was the most eflective stain. 



