SEA-FISHEKIES LABORATORY. 317 



endothelium, the muscle layer and the core of loosely 

 arranged peritoneal cells. In this and in several 

 other processes in the same heart there is a large collec- 

 tion of chlorogogenous granules in many of the peritoneal 

 cells. These are shown in red in the figure, hut they are 

 naturally of a yellow colour. The granules are often 

 aggregated into small heaps, sometimes lying in a vacuole. 

 The outlines of the cells which are loaded with chloro- 

 gogenous granules are difficult to distinguish. The proto- 

 plasm of many of the peritoneal cells is vacuolated 

 and of others is granular, but the granules are very minute 

 and of a different nature from the chlorogogen granules, 

 x 500. 



Fig. 34. Transverse section of a young specimen, 

 showing the nuchal organ, below which are the two 

 posterior brain lobes, an otocyst with its contained otoliths 

 and the tube leading to the exterior, the two oesophageal 

 connectives, the buccal mass with its sheath of muscles 

 and its retractors, the retractors of the prostomium and 

 nuchal organ, the muscles of the body wall, blood-vessels, 

 &c. The upper portion of the brain lobes and the outer 

 portion of each oesophageal connective contains nerve cells 

 (diagrammatically shown in the figure). The fibrous 

 portion of these structures is dotted. x 65. 



Fig. 35. Transverse section of a young specimen at 

 the level of the openings of the glands into the oesophagus. 

 The partitions which partially subdivide the gland, each 

 formed by a fold of the epithelium lining the gland and 

 enclosing a vascular sinus, are seen. Also the muscles of 

 the body wall and their blood-vessels ; the oblique 

 muscles ; the nerve cord ; the vesicle and external opening 

 of the second right nephridium ; portions of two notopodial 

 setal sacs and the blood-vessels connected with the alimen- 

 tary canal. The ventral vessel and the two branches near 



