Z$Q J. Stephenson : Two Oligochsete Worms. [VOL. I, 



present paper ; they differ only in the fact of an extra, newly- 

 developed group of setfe in front of the constricted zone in the 

 latter specimen ; or, if the figure of C. hengalensis is compared with 

 the posterior part of fig. 5, the correspondence is only incomplete 

 as regards the number of segments at the posterior end of the 

 animal. Similarly the figure of C. hengalensis resembles the ante- 

 rior half of fig. 7 of the present paper, with this difference, that 

 very minute new setae are beginning to form in the region under 

 discussion in the latter. 



The figures of C. spongillce and C. sp. in Annandale's second 

 paper may be compared with the present fig. 4 ; the bud in 

 fig. 4 shows a few more segments than the buds in Annandale's 

 figures, the clitellum, however, corresponds to the lateral ex- 

 pansion of the nerve-cord behind the eighth segment in fig. 4 ; the 

 length of the interval between this and the next and more promi- 

 nent constriction appears to be two fully developed segments in 

 C. spongillce, three in fig. 4, four in C. sp. 



The nature of the change at this region also appears to corres- 

 pond ; the clitellum is not a specially protuberant region, as 

 in other Naididae, but appears to be somewhat, if only slightly, 

 constricted, and the figures appear to give evidence of a slight 

 superficial transverse wrinkling of the skin. This is comparable 

 with what occurs at this situation in C. pellucidus. In Annandale's 

 figures, again, the alimentary tract is somewhat blurred and in- 

 definite at this region ; I have found this to be the case on account 

 of the lateral upgrowths of nervous matter, and also because of a 

 closer connection between the tract and the body-wall. 



The statement that the clitellum exists even in young ani- 

 mals just separated (in C. hengalensis) may be compared with 

 what was -stated above, that even the youngest free animal {cf. 

 text-fig. 2 and pi. x, fig. 3) shows the commencement of formation 

 of a zone of budding behind the eighth segment. The fact that 

 the clitellum is achaetous may be explained by a reference to fig. 

 7 ; the extremely minute newly developing setae of this specimen 

 would have been absent had it been examined a little earlier, and 

 would not have been detected as it was, had not a high magni- 

 fication been employed. 



I have not, even in the sexual animal, noted a clitellum ; 

 the zone of budding, the nature of which is evident, occurs however 

 in the same place. But I wish to guard against saying that a 

 clitellum does not occur ; it probably develops later ; in Nais and 

 Pristina, according to my observations, it is not present until the 

 genital products are far more conspicuous than the}^ are in the 

 sexual Chcetogaster above described. And I would mention, in 

 conclusion, that the Limicolae have (so far as known) the clitellum 

 on the genital segments themselves ; a clitellum in ChcBtogaster 

 on the tenth and eleventh segments would be much posterior to 

 the genital segments. 



The above comparisons seem to me to show that the structures 

 described by Dr. Annandale and myself in different ways are really 



