398 T. B. ROSSETER ON EXPERIMENTAL INFECTION OF DUCKS. 



worms as Taenia. This has been caused by the absence of a 

 definite plan, or mutual system, which would meet the varied 

 ideas and views of helminthologists ; and Dr. Railliet, in conjunc- 

 tion with Dr. Blanchard of Paris, formulated the idea, with a 

 view, no doubt, of bringing order out of chaos, and of describing 

 the genus according to the character of the hooks of the Scolex. 

 Thus, taking Tcenia coronula as a type, they propose to call it 

 " Dicranotamia " or the " forked-hooked Taenia," Figs. 1 and 2 ; 

 and Tcenia gracilis, Drepanidotcenia, or the " sickle-shaped 

 hooked Taenia," Figs. 5 and 6. I have long held the opinion that 

 the hooks of the Scolex, so variably constituted as they are in 

 form and size in each species of tapeworm, should play an im- 

 portant part, as a distinctive feature, in classifying the armed 

 Taenia in the cysticercoid stage ; and this division of Railliet and 

 Blanchard cannot but meet with approval, as it in some measure 

 meets the case, and Dr. Stiles, so far as the hooks of the tape- 

 worm are in question, adopts their views in his work. 



Stiles cites four different methods of work — i.e., 



1st. Experimental infection of poultry by feeding to them 

 known larval stages found in invertebrates, and thus raising the 

 adult stage. 



2nd. Experimental infection of invertebrates by feeding to 

 them the eggs of tapeworms found in birds, and thus raising the 

 larval stage. 



3rd. Comparison of the hooks upon the heads of adult tape- 

 worms of birds with the hooks of larvae found in invertebrates, 

 and thus associating the young and the old stages. 



4th. Wild speculation as to the intermediate hosts, based upon 

 negative results, and totally devoid of any scientific foundation. 



The first two give positive proof of the life history when the 

 experiments are successful ; the third gives, according to Stiles, 

 a probability, but not a proof ; and, to use his (Stiles') words, the 

 less said about the fourth the better. 



Grassi and Rovelli (1888, 1889, 1892), by feeding chicken with 

 slugs — Limax — containing Larvae or Cysticercus, produced Da- 

 vainea proglottina ; and myself in 1891, by feeding ducks with 

 Cypris containing Cysticercoids of an undescribed tapeworm, pro- 

 duced Echinocotyle Rosseteri, and thus fulfilled the requirements 

 of Stiles' first proposition ; and these, at the time he published his 

 work, were the only " two " instances of direct infestation known 



