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Show 440 MR. F. E. BEDDARD ON THE [Nov. 5, far as these points are concerned, it seems clear that in Macropusmajor the semen passes inwards by the lateral canals, even when the opening into the median canal exists, and in Osphranter erubescens that the embryo passes out by the median canal; but in view of the differences of structure and relations of the different parts that have been observed in different genera and species, it is not yet safe to s iy that these statements constitute a rule for the whole of the Macropodidae. 5. Contributions to the Natural History of au Annelid of the Genus Dero. By F R A N K E. BEDDARD, M.A., F.Z.S. [Eeceived September 25, 1889.] I have had the opportunity lately of observing the sexual form of a species of Dero, which I identify with D. perrieri. A large number of these Annelids made their appearance in some water containing Chara which I received from Messrs. Bolton of Birmingham ; at the end of August all, or nearly all, were sexually mature. As there appears to be no account of the reproductive organs of this worm extant, I think it worth while to publish the present notes. Except as regards the sexual organs, they are for the most part confirmatory of Perrier. The worms reached a length of about half an inch; they were extremely active in their habits, wriggling about very much after the fashion of a free-living Nematode; the colour appeared to the naked eye of a dark violet posteriorly ; in front the development of the clitellum and of the sexual products produced an opaque yellowish-white appearance. The eggs could be distinctly seen and counted with an ordinary hand-lens ; they lie behind the clitellum ; I observed the number to be almost constantly three. I have made no observations upon the tube, which, according to Perrier (" Histoire naturelle du Dero obtusa," Arch. Zool. exp. t. i. (1872) p. 65) and Bousfield (" The Natural History of the Genus Dero," Journ. Linn. Soc. vol. xx. (1887) p. 91) are fabricated by the worms. The fact that they make for themselves an habitation of this kind distinguishes the genus Dero from Nais, to which all recent writers concur in regarding Dero as closely related. The new facts which are brought forward in the present communication strongly support that view of the affinities of the worm, which may indeed now be regarded as fully established. The general anatomy of the worm has been described chiefly by d'Udekem ("Nouvelle Classification des Annelides setigeres abranches," Bull. Acad. Roy. Beige, t. xxii. pt. 2, p. 549 et seq.), Perrier (loc. cit.), and Bousfield (loc. cit). Stole (" Dero digitata, O. F. Miiller, Anatomickaa histologicka studie," SB. bdhm. Gesells. 1885, p. 65), in a paper overlooked by Bousfield and omitted from an otherwise tolerably complete list of papers dealing with Dero, has contributed details of importance, being apparently the first to have made use of the section method. I refrain from attempting |