.The Duthiersia material at my disposal is clearly divisible into five, and probably seven, distinct species. Four of these species are Asiatic forms and are, on the evidence at present available, distinguished from the African forms by the possession of posterior pores in the scolex, but this association of a small though definite anatomical feature with geographical distribution can hardly be regarded as a distinction which will hold for all Asiatic and African species yet to be discovered. Duthiersia expansa Perrier is a species distinguished from D. venusta, sp. n., the other common Indian species, by its relatively slender strobila and great length in some examples, form of scolex, presence of unsegmented neck, smooth proglottids, and flat ovary in transverse section, D. venusta being relatively a short stout form, with a very characteristic scolex, lack of neck, wrinkled proglottids, and U-shaped ovary in transverse section. Duthiersia sarawakensis, sp. n., from Sarawak, is distinguished from the preceding two, and most or all other species, by its form of scolex, total absence of elongated proglottids, and multiplicity of excretory canals. Duthiersia crassa, sp. n., the remaining Indian species, is also distinguishable from all other species by its form of scolex. Duthiersia elegans Perrier is distinguishable from all other species chiefly by its slender translucent strobila, very elongated hind segments, and presence of calcareous corpuscles, while Duthiersia robusta, sp. n., is unique in that the bothrial grooves of the scolex extend down nearly to the scolex base. A seventh species, Duthiersia latissima, sp. n., is probably represented by an African worm supplied by Professor Leiper and by portions of three strobila^ contained in the Wellcome Bureau collection, the chief features of this species being the great breadth of the gravid segments and the absence of elongated segments, the length of the full-grown strobila as a whole, and the form of the scolex.