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 Biihlmann's filaments 

 (buccal Algse) 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, Helminlha achcethelminthica .- animalia evertebrala, 

 inarliculata (i. e., exlremilalibus arliculis nullis prcedita), nunc 

 mollia, aut elaslica, ebranchiala, setis relraclilibus nullis ; whilst 

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

 Helminlha ch&lhelminlhica, i. e., animalia everlebrala, inarliculala, 

 nunc mollia, ebranchiala, vel branchiis exlernis munila } setis re- 

 tractilibus inslrucla. 



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

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



A. Plalyelmia = Flat worms. 



B. Nemalelmia = 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. Cesloidea, Vogt = Cephalocolylea, Diesing = Flat- worm 

 colonies, or Plalyelmia colonias exhibenlia, Kiichen- 

 meister. 



2. Trematoidea, Vogt = Myzelminlha, Diesing = Isolated 

 Flat-worms, or Plalyelmia isolala, 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 



