TRICHOCEPHALUS DISPAR. 321 



Mas : tenuior quam femina ; pe?iis simplex? ; organou copula- 

 torium auxiliare spinosum, ex 3 branchiis compositum. 



Femina : mare major et crassior ; vagina musculosa in abdo- 

 mine sese aperiens ; uterus simplex ; ovarium simplex. Animalia 

 ovipara, vix aut rarissime vivipara. 



Ovula oblong a, subfusca, in utroque extremitate collo quodam 

 parvulo prominente ornata (en une sorte de goulot court, 

 Dujardin). 



1. Trichocephalus dispar, with its progeny known as Trichina 

 spiralis (Owen and Luschka). 



As we shall endeavour to show in what follows that the 

 Trichocephali and Trichina are related together, we have first of 

 all to indicate the various places in the system to which these 

 two Entozoa are usually referred. Diesing in his f System' treats 

 of Trichocephalus dispar in the place just referred to, — XLIII, 

 Trichocephalus, Species 1 ; and Dujardin, as Species 1 in his 

 sixth genus. Trichina, however, is placed by Diesing in the 

 Subordo II, Proctucha ; Tribus II, Agamonematoidea {tr actus 

 cibarius proprius simplex liber. Organa genitalia nulla) ; IV, 

 Trichina, Owen {corpus capillare teretiusculum), as No. 1, Tri- 

 china spiralis, whilst the meritorious Dujardin places it, and 

 certainly with perfect justice, in his first appendix to the nema- 

 tode worms (Nematoides vrais, qui ne peuvent etre classes sure- 

 ment dans les precedentes sections des Nematoides), as a genus 

 unprovided with a number. Although the conviction has been 

 constantly gaining ground that the encysted, asexual nematode 

 worms are only the young of known species of Entozoa in course 

 of migration (a circumstance entirely ignored by Diesing in his 

 classification, which is founded rather on the external form than 

 on the embryology and development), very few attempts have 

 been made to arrange these asexual round-worms with their 

 mature parents, or, to speak more correctly, to discover the 

 mature parents of these nematode worms, and thus to free the 

 classification of these Entozoa from unnecessary names, and 

 entirely get rid of superfluous genera. The course to be adopted 

 in this ease is the same as that which we have already 

 followed with the Cestodea, and which we have indicated as 

 necessary to be followed with the Trematoda. In the attempt to 



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