050 MR J. T. CUNNINGHAM AND MR G. A. RAMAGE ON THE 



to this the tube, which is placed longitudinally, narrows ; but at the anterior end, 

 which lies near the posterior extremity of the one in front, the tube is of con- 

 siderable width. Across the internal side of the anterior portion, that is on the 

 side turned towards the body-cavity, lies a membranous appendage, whose 

 edge, which is turned towards the median ventral line of the animal, is seen to 

 be furnished with a conspicuous vascular fringe of a bright red colour. The 

 anterior extremity of the fringe is seen to be connected with a transverse 

 blood-vessel passing from the body-wall immediately behind the dorsal fascicle 

 of setae, and proceeding to the ventral vessel. From this transverse blood-vessel 

 the whole organ probably receives its blood supply. The nephridium is con- 

 fined beneath the bands of oblique muscles, which pass from the ventral 

 nerve cord to the lateral body-wall. When these are cut through, the whole 

 nephridium can be removed without difficulty ; and examination of the mem- 

 branous appendage shows that it is double, consisting of two membranes, 

 between which is a long slit-like aperture leading into a membranous funnel 

 which opens into the interior of the nephridial tube. The vascular fringe forms, 

 in the original position of the parts, the dorsal border of this internal or ccelomic 

 aperture, while the ventral border is entire and non- vascular. Both edges of 

 the aperture, including the processes of the fringe, are covered with short cilia, 

 while insii 3 the aperture are seen very long cilia which extend throughout 

 the tube. 



In 1808, when Claparede's Chetopodes du Golfe de Naples was published, 

 the gonads of Arenicola were unknown. Claparede says that most authors 

 had assigned the nephridia to the generative system, sometimes under the name 

 of ovaries, sometimes under that of testes. Quatrefages (Histoire Nat. des 

 Anneles) called them genital organs. Grure had assured himself that the 

 ovaries were not to be sought in these organs, for he had seen the ova formed 

 on the wall of the vascular caica of the perivisceral cavity ; he was inclined to 

 regard the nephridia as testicles. Claparede says this is impossible, because 

 Arenicola has the sexes separate ; he was of opinion that Grure was right as 

 to the formation of the ova, and he gives a figure of one of the caecal pseud- 

 hsemal vessels with a layer of cells surrounding it. He then leaves the question 

 of the genital organs, and proceeds to give a not very accurate description of 

 the nephridia. We were for some time at a loss as to where the genital 

 products really took origin. In February we found two or three specimens 

 which had a few ova in the body-cavity ; in these cases, and in other specimens 

 where mature ova were not present, loose cellular masses were often found 

 in the neighbourhood of the nephridia, and against the posterior wall of the 

 septum between somites 4 and 5. After considerable search, these masses were 

 traced to a cord of cellular tissue attached to the membranous funnel of each 

 nephridium. In most specimens the cells of this cord were so small and so 



