THE EXOQONKJ:. 233 



internal to the base of the corresponding ventral cirrus) on which the ducts 

 of the ventral pedal gland open. A mass of the secretion of the gland in 

 question has collected within the gland : this must be pressed out, presumably 

 as a result of the same contraction which leads to the discharge of the ova, 

 and forms a viscid plug to which the ovum becomes fixed. 



The position assigned by Viguier (34) in his description and figure (p. 89, 

 pi. 4. fig. 19) to the discharged ova of E. gemmifera corresponds very closely 

 to what I find to be the arrangement in E. fasti/era. He is not right, how- 

 ever, in the statement that the point of attachment corresponds exactly to 

 that of the opening of the " vesicule seminale " of the male : it is dis- 

 tinctly behind that point. 



The sequence of events in the male is more complicated, and I have not 

 been able to follow it out completely. The original simple, nearly straioht, 

 obliquely directed tube of the nephridium begins to become complicated in 

 the manner described below. At this stage there is as yet no appearance of 

 sperms. Later, when a mass of sperms has appeared, the pair of nephridia 

 are represented by much looped tubes with walls of the chaoteristic small 

 cells. Subsequently the sexual segments have their ccelomic cavities (en- 

 larged by the extreme attenuation of the intestine), with the extensions into 

 the parapodia, filled with sperms — the nephridia in each segment now beino- 

 represented by a single sac (PI. 18. fig. 45), apparently containing only a 

 watery liquid with which it remains distended, and communicatino- with the 

 exterior laterally by the nephridiopores. Sperms subsequently enter the 

 nephridial sacs — presumably through the ciliated funnels. From the fre- 

 quency with which this stage is met with it would appear to last for some 

 time — the huge stock of accumulated sperms gradually beino- drawn into 

 the nephridial sacs and becoming passed to the exterior. 



When the male nephridia first appear they are developed as hollow in- 

 growths from the surface in the position of the nephridiopores. Each of 

 these grows obliquely forwards and inwards, and becomes completed by 

 passing through the mesentery and terminating in the ciliated funnel, which 

 seems to be independently developed. The nephridium has now the character 

 of a straight, or nearly straight, tube running obliquely from the nephridio- 

 pore on the ventral side of the segment a little in front of the parapodiuni 

 to the nephrostome opening into the cavity of the segment next in front. 

 Its wall, as in the case of the female, is composed of a sino-le layer of 

 small cells. The terminal part of the tube is dilated into a contractile sac as 

 in the female. 



The first change that takes place is the giving off of a branch from the sac 

 not very far from its external opening (PI. 18. figs. 41 & 42). This grows 

 backwards and becomes thrown into a loop. At the same time the original 

 tube is drawn out into a loop which extends inwards and nearly meets its 

 fellow of the opposite side in the middle line on the ventral side of the 

 intestine. 



