164 On the Nephndium of Nephthys cajca, Fabr. 



I have not been able definitely to determine whether the 

 solid excretory matter before being transferred to the nephri- 

 dial tube is dissolved by the phagocyte or not ; but most of 

 the evidence suggests that it is. The green matter in the 

 walls of the canal has the appearance of minute droplets 

 rather than of solid granules, while only in one case have I 

 been able to detect a solid carmine particle in the wall, not- 

 withstanding the fact that great masses of carmine were raised 

 against it by the action of the ciliated organ. In addition, 

 the process at this point is extremely slow — specimens which 

 I have allowed to live for several days after injection still 

 showed great masses of carmine-laden phagocytes at the 

 barrier, although there were none free in the ccelom. This 

 delay seems to point to something more complicated than 

 simple transference of solid particles. 



The importance of the above process can only be fully 

 appreciated by noting the resemblance to that in the Gly- 

 ceridse, as described by Mr. Goodrich (Q. J. M. S. no. 163). 

 Indeed, if we substitute for the nephridial sac of Glycera the 

 short stretch of the nephridial tube between the ventro-lateral 

 vessel and y, the processes are largely identical. This portion 

 of the tube is evidently the physiological equivalent of the 

 sac. Morphologically it is also easy to connect the two 

 organs, the tube-barrier of JSephlhys having broadened and 

 become cup-shaped, while the ciliated organ has grown in as 

 a lining, forming a much more efficient lodgment for the laden 

 phagocytes while discharging their burdens tiian the more 

 primitive apparatus in Nephthys (Q. J. M. S. no. 163, p, 446). 



EXPLANATION OF PLATES II. & III. 



Heference letters. 



d. Dorsal blood-vessel. c.p. Vascular tuft. 



V. V^entral blood-vessel. neph.tube. Nephridial tube. 

 dl. Do ISO-lateral. c.o. Ciliated organ. 



vl. Ventro-lateral. s.t. Solenocyte-bearing tuft. 



dv. Dorso-ventral. p. Laden phagocyte. 



Fig. \. Diagrammatic transverse section of Nephthys ccsca, showing 

 position of nephridiura relative to the blood-vessels. To the right, 

 as given by Goodrich. 



Fig. 2. Dingrammatic reconstruction of the nephridiura. 



Ftg. 3. Ciliated organ and terminal portion ot the nephridium. Corro- 

 sive sublimate, sat. sol. Zeiss D. 



Fig. 4. Nephridial barrier from same. Zeiss F. 



Fig. 5. Ciliated organ and terminal portion of nephridium. From speci- 

 men injected with carmine. 



Fig. 6. Phagocytes from ccelomic fluid. Zeiss F. 



Fig. 7. Hyaline corpuscles from ccelomic fluid. Zeiss F. 



Fig. 8. Laden phagocytes. Zeiss F. 



