316 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the ventral lip. Some of these vessels have blind dilated 

 endings. The ventral lip is simple and slightly everted, 

 x 20. 



Fig. 29. Two of the processes of the dorsal lip, from 

 the second nephridium of a Laminarian specimen 190 mm 

 long, to show the multi-lobate edge. x 20. 



Fig. 30. Section of part of the excretory portion of 

 the nephridium, from a young specimen 65 mm. long, 

 showing two excretory cells with reticulate protoplasm 

 and excretory granules in the distal portion. The 

 granules become more numerous in older specimens , and 

 are apparently extruded from the distal portion of the cell 

 into the cavity of the nephridium. When this has recently 

 occurred the distal part of the cell is very clear and free 

 from granules. Each cell bears one or two long flagella. 

 Below the cells is a thin film of connective tissue (repre- 

 sented by a line) which is thicker in older specimens, and 

 outside this the thin layer of coelomic epithelium, which 

 covers the blood-vessels. x 650. 



Fig. 31. — The last nephridium of a living post-larval 

 specimen 4' 65 mm. long, in optical section. The larger 

 (right in the figure) lip of the nephrostome bears seven 

 protoplasmic processes (three are seen in the figure), 

 bearing long cilia directed towards the opening. The 

 middle of the nephridium is slightly dilated and its walls 

 contain excretory granules. The whole nephridium is 

 ciliated, x 150. 



Fig. 32. The anterior end of the same nephridium 

 drawn later. Optical section, showing the peculiar 

 ciliated protoplasmic processes of the nephrostome, the 

 cilia of the nephridial tube, and the concretions in the 

 walls of its middle portion. x 600. 



Fig. 33. A process from the heart body of a speci- 

 men 250 mm. long (see figs. 39 and 40), to show the 



