244 J. T. CUNNINGHAM. 



in these and in others in which mature ova were not present, 

 loose cellular masses were often seen in the neighbourhood of 

 the nephridia. After careful search, several times repeated, 

 these masses were traced to the cord of cellular tissue already 

 described as attached to the nephridium ; the cord of cells is 

 merely, as usual, a local development of coelomic epithelium. 

 In most specimens the cells of this cord were so undifferen- 

 tiated that it was not easy to be certain it was a gonad, but in 

 specimens which contained a few ova in the body cavity young 

 ova could be recognised in the cord. The reproductive cells 

 leave the gonad at a very early stage of development, and reach 

 maturity while floating freely in the body cavity. 



Cirratulus cirratus, Malmgren (O. F. Miiller). 



Keferstein 1 in 1862 gave a slight description of the seg- 

 mental organs in Cirratulus filiformis, Kef., bioculatus, 

 Kef., and borealis, Lam. He made out the relations of the 

 organs most completely in the first-mentioned species, in which 

 he describes them as a single pair of ciliated tubes, each bent 

 on itself, extending through segments 1 to 5, and having an 

 internal and an external opening. He gives a figure of the 

 organ as seen in the living animal, and the figure shows both 

 the external and internal openings in the first setigerous or post- 

 buccal somite. Less complete descriptions and figures are 

 given of the organs in the other two species. No other 

 nephridia are mentioned by Keferstein except this pair at the 

 anterior end. 



Claparede also saw but a single anterior pair of nephridia in 

 species of Cirratulus. He says ('Ann. Chet. Naples'): " C. 

 chrysoderma, like all the Cirratuliens, has only a single pair 

 of segmental organs, opening at the second segment (first seti- 

 gerous) by an oval aperture situated on the inner side of the 

 ventral bristles. The organ is rolled in an angular spiral. Its 

 external part is narrow, but soon enlarges suddenly into a wide 

 ciliated tube. The internal opening has escaped me." 



1 'Zeits. f. wiss. Zool.,' Bd. xii, 1862. 



