NEKEHLE, 



251 



exterior by a short duct leading to a sac on the ventral surface. A long canal springs 

 from it, and ends in front by a nephrostome provided with long ciliated processes, which 

 opens into the next segment. 



Goodrich describes the segmental organ as forming a gland-like mass of coiled and 

 ciliated tube opening externally on the ventral surface at the base of the foot by a non- 

 ciliated portion, and internally by a funnel — studded with cells having long cilia (Fig. 61) — 

 into the preceding segment. He considers that the dorsal ciliated organ is a genital 

 duct, not fully developed. The recent description by Fage 1 does not materially add to 

 this information, but he advances the view that the separate dorsal ciliated organ of 

 Goodrich is to be included in the segmental series, viz., as the rudimentary " pavilion 



Fig. 61. — Optical section through the nephridial funnel of Nereilepas fucata, Sav. The long' processes on 

 the summit are external cilia, whilst the processes on the left are septa, not cilia. (After Goodrich.) 



genital" He is not inclined to think it a phagocyte organ. It is noteworthy in this 

 respect that long ago Dr. Thos. Williams credited the segmental organ in Nereis with 

 both a dorsal and a ventral opening. It may be remarked that Fage insists throughout 

 his memoir on the essential difference between the " pavilion " (which may be freely 

 termed genital duct) and the nephridium, the former being connected with reproduction, 

 the latter with excretion. 



The sexes are separate; reproductive elements shed through the body-wall. Some 

 undergo no change, whilst many species towards the period of sexual maturity pass through 

 a metamorphosis into the Heteronereis condition. In this the eyes increase in size, the 

 palps are reduced (Gravier), the prostomium is altered, and the body forms two regions, 

 viz. , an anterior in which the feet are unchanged, and a posterior bearing the genital 



1 ' Ann. Sc. Nat./ 9 e ser. ; pp. 331—347, figs. 29- 35 ; and pi. vi ; figs. 19—23. 



