CALIKOKNIA ICP DKILID.K . 29 



general outline eoiivcx. i'lie anterior margin is eonvex-deltoid, with tiie apex at the 

 exterior pore. 



The single (hicl from tiie vesicle leaves []iv. vesicle in a dilVerent manner in 

 the respective ne[)hri(lia. In the |)e[)to-nephri(lia it aseends from the center of the 

 vesicle; in the anteelitellar vesicles it leaves from the apex of the deltoid longer part 

 of the vesicle, \\\n\r. in the post(dit(dlar nephridia it leaves from the side of the vesicle 

 l)(do\v the apex. The inner stiiictnre of the ne|)liridia corresponds almost exactly 

 with that of the nephridiiun of Argilophilus, which gcunis, however, does not [)ossess a 

 vesicle. With this exception, the nephridia of the two genera might be considered as 

 almost identical. The most characteristic feature is that the short single duct from 

 the nephridio-stome after joining the nephridial body, does not enter it as a single tube, 

 but as a .spongy duct full of irregular and connecting ductules, which later on join 

 into one larger branching- canal, the ductules, or arms of which enclose the two reg- 

 ular underneath-lying ducts. At the inner bend of the duct the ductules disappear and 

 the returning lobe contains three main canals, one of which is ciliated. This arrange- 

 ment remintls us greatly of the one observed in certain leeches and described by 

 Bourne. The vesicles consist of an outer muscular layer, which extends all around 

 the bladder, and from it, along the duct through the clit(dlnm or body-wall, to the 

 exterior pore. Between it and the c(jecal epithelium there is a continuous row of 

 connecting chambers probably analogous with the ductules of the ducts. This epithe- 

 lium is furnished with some few blood-vessels. The duct from the bladder to the 

 nephridio-pore is not otherwise differentiated, the glandular cells of the clitellura joining 

 directly on the muscular duct. Before reaching the pore but while in the body-wall, 

 the duct is enlarged, forming a small pear-shaped urinai'y bladder, which again opens 

 into a narrow duct surrounded by a row of long tubular cells, which open directly 

 into the duct. These cells form a veritable collar, the upper cells lining the inner 

 surface of the nephridio-pore (fig. 49). This in the clitellar nephridia. In the 

 nephridia posterior to the clittellum, the long tube between the vesicle and the pore 

 is entirely wanting, the bladder connecting directly with the collar of tubular cells 

 (fig. 50). The tubules, or vacuols, in the vesicle collect into at least two tubes, which 

 run downward between the muscular and glandular layers of the vesicle and appar- 

 ently open on either side at the beginning of the collar at the nephridio-pore (figs. 40 

 and oO). The secretion from this glandular layer of the bladder may be of such 

 nature as to facilitate the ejection of coarse matter such as calculi which are found 

 often in enormous quantities in the vesicle or seen as just ejected through the pores. 

 The single duct which leads from the bladder to the nephridial body proper or the 

 folded canals, apparently does not connect directly with the ductules or vacuols of 

 the bladder, but opens directly into the large central chamber of the bladder, which 

 again connects directly with the collar of the nephridio-pore. For a more detailed 

 account of the canals of the nephridia in these two genera see the description of next 

 genus, Argilophilus. Below the nephridial collar in Delinnia clcr/ansis found a large 

 branching body, probably a ganglion. It sends out branches to the nephridial collar, 

 though in my sections I have not seen their actual connection with the collar. In 



