262 J. T. CUNNINGHAM. 



filigera to be formed of several longitudinal bands, but on 

 studying sections saw that it was really a cylinder (boyau) 

 with longitudinal folds. In Terebella flexuosa the brown 

 substance forms two lobed masses, one applied to the superior 

 part of the vessel the other to the inferior. These two masses 

 are not independent, but united at intervals by thick con- 

 necting cords. In the brown organ of Audouinia the highest 

 powers only enabled him to distinguish very fine coloured 

 granules scattered in a fundamental mass. He thinks it pos- 

 sible that these brown cords are similar to the chloragogenous 

 substance which surrounds the exterior of the ventral vessel in 

 the Sabellidse, remarking that in species where the cardiac 

 body is present chloragogenous tissue is wanting, and there 

 would thus be internal as well as external deposits of 

 chloragogen. 



Horst gives some account of the minute structure of the 

 cardiac body in Brada. He describes it as made up of irregular 

 cords, each of which has usually an oval section, and is made 

 up of cells filled with brown granules. The limits of the cells 

 were not always clear, and in adult specimens only a network 

 of fibres could be seen in a section, nuclei being visible at the 

 nodes of the network, and brown granules scattered through 

 the ground substance of the meshes. I have examined the 

 minute structure of the cardiac body in several species, with 

 results slightly different to those of Horst. 



(a) Fam. Chlorh^emidjE. 



In Trophonia plumosa, when the heart is examined by 

 means of either transverse or longitudinal sections, the some- 

 what cylindrical cords of which the cardiac body is composed 

 are seen not to be composed entirely of cells as described by 

 Horst, but in most cases to be tubular, each possessing a lumen 

 (figs. 18, 19). The cells around the lumen form a glandular- 

 looking epithelium composed of several layers of cells; those 

 nearest the basement membrane are solid and nucleated, and 

 contain a large number of small, round, brown grains. The 

 more internal cells are clear and vacuolated, and the nucleus 



