302 OLIGOCHAETA 



uniting the dorsal and ventral trunks of its segment. At present there are only 

 three other Oligochaeta in which branchial processes exist, viz. Dero, Branchiura, 

 Hesperodrilus branchiatus, and Alma nilotica ( = Digitibranchus niloticus); it is not, 

 however, yet certain whether the latter worm is really an Oligochaet. 



The setae of Chaetobranc-hus are arranged as in Pristina and Naidium, that is 

 to say, there is no cephalization ; both the dorsal and ventral bundles commence in 

 the second segment. The dorsal setae are of two kinds; there are long capilliform 

 setae, which vary in length, being longest in some of the anterior bundles ; in the 

 posterior bundles there are in addition sickle-shaped setae which have a straight 

 shaft, and a curved, sickle-shaped extremity ; these two extremes are connected by 

 intermediate forms. The ventral setae are all uncinate ; there are four to six of 

 them in each bundle. 



The viscera do not present any features of special interest. The alimentary 

 canal differs from that of most Naids in having no glandular ventricle. Nephridia 

 are present, but there are no data as to the segment in which they commence. 

 BOURNE says that they resemble the nephridia of Naids generally. The coelomic 

 corpuscles are round, and contain numerous olive-green granules ; as they can pass 

 from segment to segment, it is evident that the septa must be imperfect. 



The vascular system consists of the usual dorsal and ventral trunks, which are 

 connected in each segment by a pair of lateral vessels. The dorsal vessel is much 

 pigmented. 



There are no eye-spots. 



Of the generative organs, unfortunately, nothing is known. The genus only 

 contains one recognizable species at present, viz. 



Chaetobranchus semperi, BOURNE. 

 C. semperi, BOURNE, Q. J. M. S. vol. xxxi, p. 88. 

 Definition. Length, 25-50 mm. Branchial processes, 60-70 pain. Hal. Madras, 



This species, of which a general account is given above, was discovered by BOURNE 

 in a 'tank' in Madras town 1 . It lives in the weed, moving about freely, and not 

 constructing any tube, though forming a burrow. All the individuals found were 

 in an active state of multiplication by simple fission, and were in no case sexually 

 mature. BOURNE considers that this Naid is either identical with, or closely allied 

 to, the worm described by SEMPEK (1) as occurring along with Dero philippinemds. 



1 I found specimens in the Victoria nyia tank at the Botanical Society's Gardens, Regent's Park. 



