264 J. T. CUNNINGHAM. 



branched part coming into contact with the dorsal and lateral 

 sides of the heart. The organ also differs from that of Tro- 

 phonia in minute structure. In transverse section the band is 

 narrow and branched ; that is to say, the main band gives off 

 other longitudinal bands of less extent than itself, so that in 

 transverse section it appears as an irregularly branched narrow 

 tract. No distinct lumen is visible in the centre of this tract, 

 but there is a distinct central line which separates the epithelia 

 of opposite sides where they come into contact. The clear 

 vacuolated cells seen in Trophonia are here absent, the epi- 

 thelium consisting of elongated columnar nucleated cells only ; 

 the granules are smaller and less numerous (fig. 20). 



Fam. TerebellidjE. 



In Amphitrite Johnstoni the cardiac body occupies 

 nearly the whole cavity of the heart, the channels left for the 

 passage of the blood being very small. It is composed of 

 cylindrical cords which generally have a longitudinal direction. 

 In prepared sections no lumen is visible in the cords, each 

 being completely filled with a mass of cells whose outlines are 

 somewhat indistinct, but the nuclei are large, spherical, and 

 deeply stained. The cells are small, so that the nuclei are 

 closely crowded together. In Amphitrite cirrata and 

 Terebella Danielsseni the cardiac body exists, but I have 

 not specially examined it. 



In Lanice conchilega the cardiac body is smaller in rela- 

 tion to the heart than in Amphitrite Johnstoni. The 

 cords are thinner, and confined to the immediate neighbour- 

 hood of the walls of the vessel, so that a large central space is 

 left for the passage of the blood. In the cords a lumen 

 is frequently but not always visible. The cells have a 

 similar character to those of Amphitrite Johnstoni 

 (fig. 14). 



In Terebellides Stroemi there is but a single cord in the 

 cardiac body, which runs longitudinally and fills up very nearly 

 the whole cavity of the heart. In prepared sections a lumen is 



