32 T. B. ROSSETER ON THE TAPE-WORMS 



"oval-embryo" in either case possessed (Extrait du Bulletin de 

 VAcademie des Sciences de Cracovie) ; whilst B. H. Ransom (Studies 

 from Zoo. Lab. Univer. Nebraska, U.S.A., 1902) places Conard's 

 new species of tape-worm, from a chicken, with unarmed rostellum 

 but with armed suckers, not in the genus Davainea as the armed 

 suckers would indicate, as Conard in his manuscript suggested, 

 and as Magalhaes, who had previously discovered the worm and 

 described it in Arch, de parasit., i., pp. 442 — 449, had already 

 done, but, its structural resemblance to the type of Hymenolepis 

 being so great, in that genus under the name of Hymenolejris 

 ■carica (Magalhaes). 



The specimens of Taenia nitida that Berg submitted to Krabbe 

 were in every respect perfect specimens, and possessed the onco- 

 sphere or six-hooked brood. On Plate 6, fig. 135, Krabbe figures 

 the same, and from his description the oncosphere of T. nitida 

 possesses but one individual or single membrane "en enkelt hind"; 

 Plate 5, Fig. 16, is a facsimile of his figure. Now, although in 

 his diagnosis of this genus Blanchard explicitly says that the eggs 

 are " entoures de trois coques tres ecartees les unes des autres," 

 still, I do not consider that the fact of the embryo of T. nitida 

 being enclosed in but one envelope excludes it from being placed 

 in the genus Hymenolepis. It is permissible to suppose that the 

 other membranes of the eggs may have been overlooked by 

 Krabbe in his investigations, from the possibility of the inner 

 or median membrane being closely applied or adherent to the 

 outer envelope, and thus having escaped detection ; and the third 

 envelope might have been invisible owing to the embryo filling up 

 the whole of the cell cavity, and possibly from the want of differ- 

 ential staining to discriminate between the plastic substance of 

 the embryo and the enveloping membrane. The first instance, or 

 adhesion of the median membrane, is illustrated in the case of 

 Ransom's oncosphere of H. megalopts (Nitzsch), where the median 

 envelope is only brought into view by being drawn away from 

 the outer envelope by osmotic pressure. Should such not be the 

 case, and should future investigation of this species demonstrate 

 that the oncosphere does in reality possess but one enveloping 

 membrane, I should be even then, as I am now, of opinion that 

 the possession of three testes and its structural resemblance to 

 the type of Hymenolepis justifies T. nitida being placed and 

 retained in that genus. 



