ON THE NEPHEIDIA OF THE POLYCH^ETA. 193 



From the above description it appears that in Nephthys 

 there is no internal opening to the nephridium, which ends in 

 a bunch of short blind branches. The current in the lumen 

 of the tube produced by the flagella of the tube-bearing cells 

 and the cilia along the canal travels from the terminal branched 

 organ towards the external pore. It seems obvious^ then, that 

 excretion must take place through the walls of the nephridium 

 as it does in these organs in the Platyhelmia and Nemertina. 

 Possibly the thin-walled tubes in which the flagella work act as 

 osmotic filters, allowing liquid to pass through from the coelom. 

 Solid excretory products are more probably conveyed to the 

 lumen of the canal by the cells themselves. The wall of the 

 nephridial canal often contains such a number of granules as 

 to appear of a distinctly brown or greenish hue. 



A discussion of the bearing of the facts described above on 

 the question of the morphology of the nephridium and ciliated 

 organ is reserved for a second paper, in which it will be shown 

 that the nephridium of the Glycerids is built on essentially 

 the same plan as that of Nephthys, with flagellated " tube- 

 bearing" cells. 



EXPLANATION OF PLATES 6—9, 



Illustrating Mr. Edwin S. Goodrich's paper " On the Nephridia 



of the Polychaeta." 



List or Reference Letters. 



ac. Aciculum. at. v. e. Attached ventral edge of the ciliated organ, b. w. 

 Body-wall. c.ep. Ccelomic epithelium, c.f. Ciliated furrow, cil. Cilia. 

 CO. Ciliated organ, ccel. Ccelom. coel.corp. Ccelomic corpuscles, c.r. 

 Ciliated ridge, cut. Cuticle, c. w. int. Cut wall of the intestine, d. I. m. 

 Dorsal longitudinal muscles, dl. v. Dorso-lateral vessel, dp. v. Dorso-pedal 

 vessel, d.v. Dorsal vessel, dv.v. Dorso-ventral vessel, epid. Epidermis. 

 /. d. e. Free dorsal edge of the ciliated organ. /. Flagellum. go. Gonads. 

 int. Intestine, irr.m. Iridescent muscle, t.v.v. Left ventral vessel. In. 

 Lumen, m. Muscle, n. Nucleus, n. c. Nerve-cord. ne. Neck-like pro- 

 VOL. 40, PART 1. NEW SER. N 



