DESCRIPTIONS OF GENERA AND SPECIES 665 



transverse and longitudinal sections of the integument; Perrier has figured these 

 bodies as lying in involutions of the cuticle; they are, he thinks, of a glandular 

 nature — are to be compared with the unicellular glands of the Articulata; Vejdovsky 

 (3) has pointed out that there is a considerable similarity between these bodies and 

 the large cells of the Enchytraeid Anachaeta ; these latter occupy the position of 

 the missing dorsal setae of that worm (see p 354), and represent the seta follicles. 

 This suggestion is certainly, on the whole, borne out by the appearance of the cells 

 in question, in Pontoscolex, and also supports my contention that worms with few 

 setae in each segment have been derived from a PericAaeto.-like form ; that the 

 integumental bodies of Pontoscolex do not always form a regular row between the 

 setae does not so far weaken that view of the homologies of the bodies ; for in 

 Perichaeta the setae occasionally form slightly irregular rows. My comparison (62) 

 of the integumental bodies of Pontoscolex to the epidermic sense organs of the 

 Eudrilidae no longer commends itself to me. 



The vascular system of this worm is beautifully illustrated in Perrier's memoir; 

 some of these figures are repeated in the present monograph (woodcuts, figs, ao and 21). 



In this place I shall only mention the principal features of the circulatory 

 system which are of systematic importance ; for further details the reader is referred 

 to the account of the vascular system of the Oligochaeta on p. 64 et seq. The dorsal 

 vessel communicates with the ventral vessel by three vessels in the eighth, ninth, 

 and tenth segments ; in the two following segments are two pairs of very much 

 dilated ' intestinal hearts,' which put the supra-intestinal trunk into communication 

 with the ventral vessel. Behind this segment there are no branches uniting the 

 dorsal with the ventral vessel; but there are slender twigs which join the dorsal to 

 the subneural vessel ; anteriorly there are a pair of lateral vessels. 



The nephridia consist of a series of paired tubes, as in all other Geoscolicidae. 

 In the anterior part of the body one of these pairs is very much larger than those 

 which follow; it was termed by Perrier the 'Glande a mucosit^.' The structure of 

 this first pair of nephridia was imperfectly described by Perrier ; I subsequently 

 added a few details upon its minute anatomy, showing conclusively that the gland 

 is a nephridium (71). In many earthworms the anterior nephridia are thus enlarged 

 and are occasionally connected with the buccal cavity. In Pontoscolex, however, 

 the nephridium opens on to the exterior upon the second segment of the body ; the 

 anterior extremity of the body is so retractile that the aperture sometimes comes to 

 lie within a temporary buccal cavity. A long muscular duct connects the external 

 pore with a tuft of tubes lying closely pressed against the oesophagus on either side ; 

 these open into the body cavity by two or three funnels on each side. It is possible 



