niYIA'M ANNULATA 



M)7 



leads by a narrow ciliated duct into a receptacle, in which leuco- 



cytes ladeii with waste-matters are -received from the ccelomir 



spaces and sinuses, subsequently 



to undergo degeneration and 



absorption (Fig. 422). By its 



outer side this receptacle is in 



close relation to the inner end 



of the nephridium, and the 



waste-matters from the disin- 



tegrated leucocytes are no doubt 



received into the nephridial 



canals and thus passed out to 



the exterior. In Hirudo and 



Herpobdella (Nephelis) the re- 



ceptacles appear to be the 



organs in which new blood- 



corpuscles are manufactured. 



The ciliated funnels of the Hiru- 



dinea correspond more closely 



with the ccelomoducts or ciliated 



organs of the Polycheeta than 



with the nephrostomes ; they 



are to be compared also with the 



" urns " of the Sipunculoidea. 



In the Rhynchobdellid Ponto- 



bdella a very interesting modifi- 



cation of the nephridial system 422 



occurs. Instead of distinct neph- 



ridia, there is found on the 



ventral surface of the body a 



very complex network (Fig. 423, 



uph.), which sends off on each side of each segment a short branch 



terminating in a ciliated funnel, and 

 a similar branch which opens ex- 

 ternally (np.). A similar modifica- 

 tion occurs in Branchellion. 



The nervous system always 

 closely resembles that of Hirudo, as 

 also do the sense-organs. The 

 number of eyes is subject to con- 

 siderable variation : they may be 

 developed on the posterior sucker, or 

 may be absent altogether. 



Reproductive Organs. The 

 testes usually have the segmental 



' c . .,,. -P 



arrangement lound in Hiruno, their 

 "umber varying from five to twelve 



Ciliated funnel of Herpobdella 

 (Clepsine). cr. crown-cells of funnel ; ex. 

 terminal cell of the nephridium ; Ic. leuco- 

 cytes ; st. duct leading to receptacle ; w. wall 

 of receptacle. (From Meisenheimer, after 

 L. von. Graff.) 





G- ^J- Nephridial system of Pon- 



tobdella. fin. 14, fin. 17, gangliu 



of nerve-cord ; p. nephridiopore ; 



Ci "' 



