coe: nemerteaxs of west and northwest coasts. 



43 



distance from mouth to intestine. In the ek:)ngated forms of Cari- 

 XELLA, Taeniosoma, Lineus, and other genera these excretory- 

 organs may be less than one twentieth as long as the body, but in 

 other forms (Nemertopsis, Stichostemma, and Geoxemertes, 

 for example) they extend throughout practically the whole length 

 of the l)ody.. Probably in no case is there any direct communica- 

 tion between the nephridia and any other vessels — the only open- 

 ings to the canals being the pores l)y which they discharge their 

 contents on the surface of the body, or, in rare instances into the 

 alimentary canal. In the majority of forms there is but a single such 

 excretory pore on each side of the body, but in other species there 

 may be as many as 20 or more. Where numerous efferent ducts 

 are present, the number increases with the size and jjrobably with 

 the age of the individual. In Stichostemma Bohmig ('98) found 

 but a single pair of nephridia in small individuals while the larger 

 specimens invariably had several. 



A. Paleonemertea. — In most species of Carinella, Carino- 



FiG. 14. — CarineUa rubra. Transverse section of body in nephridial region, show- 

 ing position of nephridia (nep), and opening of eflerent nephridial duct (nd); 

 e, stomach ; In, lateral nerve ; bv, lateral blood vessel. 



MELLA, and Carhstoma the nephridium of each side consists of a rather 

 broad canal situated in the posterior half of the esophageal region. 

 This canal becomes narrow towards its anterior third (PL 5, fig. 48), 

 and lies close against the lateral border of the thin-walled lateral 

 blood vessel. From the side of the canal very numerous short proc- 

 esses or finger-like projections push out directly against the wall of 



