1889.] 



NATURAL HISTORY OF DERO. 



443 



Nos. 5, 6, 7. The cells which compose the epidermis of the clitellum 

 are much taller than those which constitute the epidermis else- 

 where ; they are columnar in form and loaded with granules to 

 such an extent that the nucleus (in individuals stained with picro- 

 carmine) was altogether invisible. In a surface-view of a fully 

 developed clitellum the cells often appeared to project as shown in 

 fig. 2 b ; the cells of the clitellum are at first only occupied by a 

 few highly refractive granules, the cell-outline being very indistinct 

 (fig. 2 a). In longitudinal sections of tiie clitellum (fig. 2 1/) the un- 

 stained cuticle could be easily seen ; very frequently the cuticle was 

 separated from the outer extremities of the clitellar cells by a space 

 containing an amorphous substance, which in individuals coloured 

 bv picrocarmine solution was stained deep pink. I regard this 

 substance as the product of the activity of the chtellar cells, destined 

 probaldy for the formation of the cocoon ; its accumulation between 

 the cuticle and the epidermal cells seems to be remarkable, even it 

 the secretion has been caused by the stimulation of the glandular 

 cells by the preservative reagent. 



Sperm atheca. — There is a single pair of these organs situated in 



Fig. 3. 



Spermatheca of Dero in longitudinal section, sp, spermatozoa. 



the 5th segment. The apertures to the exterior are placed on the 

 boundary-line between this segment and the 4th, just in front of the 

 ventral setse. These setse were constantly two in number to each 

 bundle ; I did not observe any variation in this respect in a numher 

 of individuals. The number of setse in the ventral bundles of the 

 three segments anterior to the fifth I found to vary slightly, although 

 usually three. Exce[)t as regards their apparently fixed numher, 

 the setae lying behind the apertures of the spermathecee were in no 

 way different from those of other segments ; as in the asexual form, 

 the dorsal setse of segment 5 and of those preceding it are entirely 

 absent. 



The spermathecse were in every case distended with spermatozoa. 

 The structure is illustrated in fig. 3, which refiresents a longitudinal 

 section ; the narrow duct of the pouch is lined with an epithelium 

 of tall cells, elsewhere the cells of the lining epithelium are much 

 smaller. 



All the specimens were so fully mature that it was no longer 

 possible to recognize the position of tlie testes and of the ovaries. 



30* 



