450 JNIR. J. 11. LLUYD OX THE STRUCTURE AND LIFE HISTORY 



Historical. 



8ome confusion appears to exist as to the correct generic name 

 of the Common Nematode of Scyllkmi canicida. The first geiiei'ic 

 name assigned was Prole})i>hs by Dujardin (5) in 1845. He 

 distinguished two s})ecies — Froleptus acutus and Froleptas ohtusus, 

 but as he gives neither description nor diagram of F7'ole2)tus 

 obtusits, it may be considei'ed invalid. 



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

 IHsiiocephalus dacnodes, which should appai-ently be refei-red to 

 the genus Frolejjtus, as it differs considerably from the remaining 

 species of JJistlocephcdus and appears to be wrongly placed. 

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

 worm under the generic name of Spnroptei'ina. 



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

 was provisionally assigned by Creplin (4) to the genus Sjyiropiera, 

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

 Spiropteras of Talpa, Erinaceus^ etc. 



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

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

 Coroudla saUlicola, Coroiidla robasta, and Corondla viinida. 

 Neither the new genus nor the new species were described, but 

 six drawings were given, which referred indiscriminately to two 

 of the species — viz., Coronilla rohusta and CoroitiUa scUlicola. 



Spiropterina appears to be the generic name Ijy which the 

 worm is mo.st commoidy known, but Liiistow (7) has put forward 

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

 of priority. For this reason I shall use the generic name Fro- 

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

 distinct species which occurs in Scf/lliuui caiulus^ and his species 

 ohtusus is difficult to determine, I propose to retain Van 

 l^eneden's specific name scUlicola., and shall describe the worm 

 under the name of Froleptus scUlicola. 



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

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

 several respects, and his diagrams are inaccurate. 



Morphology. 

 (a) External Characters. 



The body is surrounded by a very thick, transparent cuticle, 

 which is finely ringed transversely. Froleptus scUlicola 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 

 Para-carmine was the most efiective stain. 



