ANIMAL PARASITES. 11 



It appears to me that there is a confusion here of the animalcule 

 with the buccal Algae, their spores, &c. An error has certainly 

 slipped in with regard to the production of Buhlmaim ; s filaments 

 (buccal Algae) from Infusoria. This metamorphosis is impossible. 

 Nevertheless I do not venture to decide whether this particular 

 Denticola exists amongst them. 



Second Class — Vermes, Helmintha (Diesing). 



The animals of which we have now to treat belong to Diesing' s 

 first sub-class, — Helmintha achathelminthica .• animalia evertebrata, 

 inarticulata (i. e., extremitatibus articulis nullis prcedita), nunc 

 mollia, aut elastica, ebranchiata, setis retractilibus nullis ; whilst 

 we find no representatives of Diesing's second sub-class, the 

 Helmintha chathelminthica, i. e., animalia evertebrata, inarticulata, 

 nunc mollia, ebranchiata, vel branchiis externis munita, setis re- 

 tractilibus instructa. 



In the consideration of the different classes, however, we prefer 

 following, as Virchow has done, Vogt's division into — 



a. Platyelmia = Flat worms. 



b. Nematelmia = Round or Thread-worms. 



And, like Vogt, again dividing the first section into two sub- 

 divisions. At the same time we would put it for consideration 

 whether it would not be better to adopt the new denominations 

 added at the end. 



a. 1. Cestoidea, Vogt = Cephalocohjlea , Diesing = Flat- worm 

 colonies, or Platyelmia colonias exhibentia, Kiichen- 

 meister. 

 2. Trematoidea, Vogt = Myzelmintha, Diesing = Isolated 

 Flat-worms, or Platyelmia isolata, Kiich. 



It will scarcely be possible to do anything further towards the 

 union of these two subdivisions than is here done, that is to say, 

 placing them together in the system in one great division. 

 Virchow represents Van Beneden as referring all the cestode 

 worms to the Trematoidea, and I myself felt compelled to attribute 

 to Van Beneden the same views, judging from the hitherto im- 

 perfectly known opinion of that illustrious naturalist ; but his 



