31 



ON THE TAPE-WORMS HYMENOLEPIS NIT/DA, KRABBE, 

 AND H. NITIDULANS. KRABBE. 



By T. B. Rosseter, F.R.M.S. 



(It- ad January 18*A, 1907.) 



Plates 5 and G. 



T FEEL justified in placing, as I have here done, two hitherto 

 uncorroborated species of tape-worms, discovered by Berg and 

 Krabbe respectively, and described and figured by the latter, go 

 far as the armature of the scolex is concerned, in his Bidrag 

 til Kwndshaby in the genus ffymenolepis, Weinland, because, 

 apart from the fact that only in the case of II. nitida has the 

 embryo or six-hooked brood been seen, the morphology and 

 physiology of these worms coincide specifically with Dr. Raphael 

 Blanchard's diagnosis of this genus ffymenolepis, Weinland [Hist. 

 Zoo.et Med. des Taeniades d/u <jr,,r< Nymenolepis, Weinland, 1891, 

 pp. 48, 49), and are analogous with his type specimen, 

 11. diminuta. I have therefore withdrawn them from the 

 Taeniidae and placed them in the genus ffymenolepis, Weinland. 

 True, an objection might be raised that in each of the species 

 under consideration the hooks of the rostellum (ten to twenty) are 

 far below the number (twenty-four to thirty) given by Dr. R. 

 Blanchard as characteristic of the genus. Numerically, this 

 objection cannot be sustained, as the genus is divided into two 

 groups, armed and unarmed. Consequently, the armature, whether 

 normally or from caducity, must necessarily vary. Dr. 0. von 

 Linstow has taken advantage of this disparity, and placed his 

 new species II. trifolium, with ten hooks on the rostellum, in the 

 genus Hymenolepis, admitting that the " Eier waren noch nicht 

 entwickelt," thus being able to give us no description of the eggs 

 (Sonder-abdruck Archiv fiir Mik. Anat., Band 66, 1905). M. M. 

 Kowalewski, too, places his new species of tape-worms — II. arcuta, 

 from Fidigula marila, and II. parvula, from Anas boschas dom. — 

 both with ten hooks on their rostellum, in the same genus ; but 

 he neither figures nor tells us in the text how many envelopes his 



