492 MR. F. K. BEDDARD ON THE [DcC. 4, 



The sexual organs of the mature worm, with a fully developed 

 clitellum, differ to a certain extent in the two species whick I have 

 studied. 



In C. ater there is a distinct and large prostate gland (Plate 

 XXIII. fig. 7), which opens into the distal extremity of the glandular 

 part of the atrium. In C. arenarius I have been unable to find such a 

 gland, and Claparede states that it is absent in that species ; he makes 

 no remark about the prostate gland of C. ater, but, as he prefixes to 

 his brief account of this species a generic definition of Clitellio, the 

 gland evidently, if present, escaped his notice. Furthermore, in 

 C. ater the glandular part of the atrium, although exhibiting the 

 same structure, is relatively smaller than that of C. arenarius ; it is 

 entirely contained \\ithin the 11th segment, and is not curved upon 

 itself. The vas deferens is very long and much coiled ; it opens into 

 a rounded chamber at the extremity of tlie atrium, the cells of 

 which (Plate XXIII. fig. 7) are different from those of the atrium 

 and more like those of the vas deferens. In C. arenarius the vas 

 deferens is much shorter and wider (cf. Plate XXIII. figs. 5, 6), while 

 the atrium is much larger; on one sideof the body, in the single mature 

 example of this species which I investigated by sections, the atrium 

 was bent upon itself and entirely contained in the 11th segment; on the 

 other side of the body the atrium extended back beyond this segment. 



The funnels of the vasa deferentia in both species are cup-shaped 

 and furnished with abundant long ciha. 



As in the Tubificidse generally the mature ova are of very large size 

 (half the diameter of the body), and loaded with yolk-spheiules : I 

 found them in G. arenarius so far back as segments 13-1 5 ; in the first 

 and last of these segments was a single ovum, in the middle one two ; 

 the ova were not freely floating in the body-cavity, but were enclosed ia 

 distinct sacs (Plate XXIII. fig. 4), furnished with blood-vessels; 

 these sacs were perfectly independent of each other, there was no com- 

 munication that I could trace between the ovisacs of adjacent segments. 



In O. ater there appeared to be a similar arrangement. The 

 spermutheccB of the sexually mature worms offer a valuable differential 

 cliaracter ; they are most complicated in C. arenarius. Claparede, 

 in his figure of the spermatheca of this species ', has correctly 

 indicated the division of the spermatheca into two parts by a 

 median constriction ; in the part which communicates with the 

 exterior only are foimd the spermatophores. The distal pouch in 

 my specimen contained a liquid deeply stained by the colouring 

 reagent ; its walls, moreover, were lined by an epithelium of a different 

 character to that found in the proximal part of the spermatheca. 

 In Tubifex rivulorum ' there is a corresponding specialization 

 of the lining epithelium, but here there is no constriction developed 

 between the different regions of the pouch. 



In Claparede's figure this constriction is not sufficiently marked ; 

 in my specimen (tee fig. B, p. 491) the two halves of the spermatheca 

 are joined by an extremely narrow neck. 



' Etudes, &c., loc. cit. pi. iii. fig. 4. 

 ^ YejdoTsky, loo, cit. pi. ix. fig. VI. 



