NEMATELMIA. 289 



class has not yet advanced so far that we can undertake an 

 exact division of them into genera, as Dujardin and other helmin- 

 thologists suppose. There is no doubt that both Dujardin's 

 attempted division into seven sections, although this recommends 

 itself strongly by its simplicity, and the extraordinarily elaborate 

 division of Diesing, in course of time, and the more they are 

 worked out according to Von SiebokPs views, will certainly 

 undergo more and more alteration. Above all, Diesing's treat- 

 ment of the nematode worms leaves much to be desired, whether 

 with regard to the indication and estimation of anatomical facts 

 (see, for example, the section Trichina, in which the primordial 

 lines of the genitalia are certainly to be found), or to the classifi- 

 cation of the round- worms, and the establishment of the separate 

 species (compare the divisions, Gordius, the 118 species of which 

 are to be reduced to 3, according to Von Siebold, or Mermis, the 

 17 species of which are to be reduced to 2, according to the same 

 authority ; or the section Nematoidewn hominis No. 2, which is a 

 Pentastomum). For these reasons I shall not adhere to a strict 

 classification. I shall select the names most generally employed, 

 and shall not observe any fixed order in the enumeration of the 

 particular species, but rather review them in accordance with 

 their dwelling-place in the human body. 



The distinct presence of a digestive apparatus, divisible into 

 mouth, oesophagus, stomach, intestine, and anus, the separation 

 of the sexes into two individuals, the certain detection of a ner- 

 vous system in some of them, and the apparently jointed structure 

 of the round worms, brings them near to the Articidata. In the 

 human subject we must take into consideration : I, the Tricho- 

 cephali and Trichina ; II, the Oxyuri ; III, the Strongyli and 

 Ancijlostoma ; IV, the Filaria ; and V, the Ascarides. 



It is not very long since it was thought that the Nematoidea 

 were the most accurately known of Entozoa, but now-a-days we 

 must admit that we have more positive knowledge of the history 

 of the development of the cestode worms, and even with regard 

 to the Trematoda possess a conjectural zoology, which has as 

 much if not more claim to probability than is the case with the 

 developmental history of most of the round worms. 



The nematode worms, or at least a great part of them, appear 

 only to be able to reach maturity when they undertake various 

 immigrations and emigrations during their youth ; one species of 

 round- worm occurring in the human body, however, as we shall 



T 



