HEKATEROBEANCHUS SHRUBSOLII. 187 



In the young specimens above mentioned (p. 182) these 

 tubes were not to be seen, showing probably that they also 

 develop late with the oesophagus. 



The second kind of nephridium is found in the abdominal 

 region of the body only of those individuals in which the 

 gonads are developed, a single pair in each segment in which 

 there are gonads. In such individuals they may be seen very 

 distinctly in transverse section (fig. 8, 7ieph.'). They are very 

 short, simple, uncoiled, ciliated tubes (fig. 14). But here, 

 again, it is very difficult to say with absolute certainty whether 

 they lead through a septum from one segment to the next, or 

 whether they lie wholly in a segment. 



In individuals in which there are no genital products 

 present they are, if represented at all, at any rate functionless, 

 and with no lumen. They serve, therefore, as genital ducts. 



Genital Organs. — The sexes appear to be distinct, 

 though I am not sure that I have seen any specimens with 

 ova. As is usual in marine annelids, the generative products 

 develop only at certain seasons of the year, and at other times 

 the males and females are indistinguishable. In living speci- 

 mens which I examined in the summer I thought I saw eggs, 

 i. e. I saw bodies resembling eggs, but forget whether I dis- 

 tinctly saw them in the coelom, or only inferred them to be 

 there. They may, therefore, have been only parasites. Un- 

 fortunately, thinking that I was sure to get plenty more with 

 eggs, I did not preserve or cut sections of any of them. 



The sperm-mother cells are oval or spherical, with well- 

 marked nuclei which may be seen dividing. Masses of them 

 may be seen in the ripe male individual on either side of the 

 intestine just above the nephridium, and attached to the 

 coelomic epithelium surrounding the sinus of the intestine in 

 all the hinder abdominal segments (fig. 8, test.). Spermatozoa 

 with long tails may also be seen. Together they occupy 

 almost the whole cavity of the ccelom in the region where they 

 are developed. In the one ripe male individual of which I 

 was able to cut sections, which was a specimen with thirty- 

 five segments altogether, the gonads (and consequently the 



