A more extended acquaintance with the African forms of Duthiersia (altogether 254 examples from Uganda, the Sudan, the Gambia, Sierra Leone, Nigeria, Portuguese East Africa, Orange Free State, and Transvaal) appears to show that, on account of intermediate conditions, all these forms must be regarded as varieties of one species, Duthiersia fimbriata (Diesing, 1854). Differences of specific value are present in this material, but are not associated to constitute species. Duthiersia elegans Perrier, 1873, and the two species instituted by me in 1938—-D. robusta and D. latissima—cannot therefore be maintained.
The study of the original 78 and of 48 additional specimens—126 altogether— of Duthiersia, mostly from the United Provinces in India, but also, in the case of a few specimens, from Calcutta and Madras and, outside India, from Sarawak and Java, leads to a similar conclusion for non-African forms, viz., that all are to be included in one species, Duthiersia expansa Perrier, 1873, the differences in structure not being segregated so as to form species.
The scoleces of African forms of Duthiersia appear, in large part, to assume shapes distinct from those of Asiatic forms, but, apart from this, the sole distinction which can at present be adduced to separate Duthiersia fimbriata from Duthiersia expansa, i. e., the African from the Asiatic forms, is the uniform absence in the former and the uniform presence in the latter of posterior pore-openings of the bothrial grooves. This statement is based on serial sections of 74 scoleces cut by me (47 African and 27 Asiatic) and on some additional evidence quoted in my original paper from Monticelli and Crety, Lühe (E. Africa), Shipley (Ceylon), Southwell (India), Klaptocz (Sudan), and Beddard. This distinction is thus founded upon a very small and inconvenient feature, but it is perfectly definite and is the only one I know of at present.