STUDIES ON EARTHWORMS. 87 



nephridiopore. These spermathecse are placed in the somites 

 VII, VIII, and ix. 



The nephridia occur in every somite behind the second 

 (fig. 17, n, n'). Those of the seven anterior somites differ 

 slightly from those in the rest of the somites. An ordinary 

 nephridium, taken from a somite behind somite ix, consists of 

 a delicate, loosely-coiled, short tubule, containing two, or in 

 some parts three, parallel lumina; the lumen communicates, on 

 the one hand, with the coelom by means of the funnel, and on 

 the other with a vesicular diverticulum, which opens to the ex- 

 terior (fig, 18). This vesicle is a long, thin-walled sac, the free 

 blind extremity of which, directed dorsally, is rounded ; while 

 the narrow duct, after receiving the tubule of the nephridium, 

 dips into the body wall and opens to the exterior by the ne- 

 phridiopore, placed in a line with the lateral setse (fig. 20, o) . 

 In the preserved condition each of these vesicles contained, at 

 their blind end, a mass of white granular substance, rendering 

 the vesicles very conspicuous on opening the worm. The 

 structure of the tubule and the shape of the funnel (fig. 19) 

 closely resemble those ofLumbricus. 



The nephridia behind somite xx are smaller, and the tubules 

 even less coiled than in the one just described. 



The nephridia in somites iii to ix present a somewhat dif- 

 ferent arrangement of their parts (fig. 17 n} — n'). The tubule 

 is less developed than in the posterior nephridia, and instead 

 of opening into the neck of the vesicle near the external pore 

 it enters the enlarged portion of the vesicle near its blind end. 

 These seven nephridia have very long narrow vesicles, since 

 the tubular portion is carried far back, and lies (as shown in 

 fig. 14, /) alongside of, and partly above, the oesophagus and 

 gizzard. A similar difference between the most anterior and 

 the following nephridia is seen in the case of Microchseta 

 Eappi. 



Pyriform Sacs. — In each of the somites behind the ninth, 

 i. e. behind the last pair of spermathecse, there is a pair of 

 small pyriform sacs (fig. 17, jp) placed between the nerve-cord 

 and the ventral setse. Each of these has its enlarged free end 



