440 MR. F. £. 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 tlie differ- 

 ences of strncture and relations of the different parts that liave been 

 observed in different genera and species, it is not yet safe to siy that 

 these statements constitute a rule for the whole of the Macropodidaj. 



5. Contributions to tlie Natux'al History of an Annelid of the 

 Genus Dero. By Frank E. Beddard, M.A., F.Z.S. 



[Eeceived September 25, 1889.] 



I have had the opportunity lately of observing tlie sexual form of 

 a species of Dero, whicli I identify with D. perrieri. A large 

 number of these Aiuielids made their appearance in some water 

 containing Chara which I received from Messrs. Bolton of Birming- 

 ham ; 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 fabi'icated by the worms. The fact 

 tl)at they make for themselves an habitation of this kind distinguislies 

 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 communi- 

 cation strongly support tliat view of the affinities of the worm, which 

 may indeed now be regarded as fully establislied. 



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 (Joe. cit). Stole (" Dero digitata, 

 O. F. Midler, Anatomicka a histologickastudie," SB. bohm. Gesells. 

 1885, p. 65), in a paper overlooked by Bousfield and omitted from 

 an otherwise tolerably complete list of i)apers dealing with Dero, 

 has contributed details of importance, being apparently the fijst to 

 have made use of the section method. I refrain from attempting 



