HEART-BODY, ETC., OF CERTAIN POLYOH^TA. 289 



heart, the heart-body extended iu two thick cords into the 

 peri-intestinal sinuses. In Terebellides Stroemii the 

 organ is hollow; but in most Terebellidse it is solid. In 

 Lanice conchilegaitisin the form of a number of cords 

 similar to those of Stylaroides. 



The colour of the heart- body in the Terebellidse is deep 

 brown, and varies in intensity with the general depth of pigmen- 

 tation iu the rest of the animal. Oval masses of coarser pig- 

 ment are set in it here and there transversely to its length. 

 The organ is enclosed in a fine endothelium, as in the case of 

 Audouinia. Cortex and medulla are not distinguishable ; but 

 the elongated cells of which the structure is composed form a 

 sort of network, radiating out from the central axis. There is 

 no great lumen ; but numerous intercellular spaces appear. The 

 pigment granules are of a greenish-yellow colour, and each is 

 usually surrounded by a vacuole (figs. 27 and 32). Each of the 

 oval patches of granules mentioned above is contained in an en- 

 velope, and perhaps represents a much-distended cell (fig. 28). 



In sections of Polymnia nebulosa numerous blood-cor- 

 puscles are to be seen in the coagulated blood in the vessels. 

 They appear to be non-nucleated ; but each contains a minute 

 granule or crystal. 



The coelomic corpuscles of Terebellidge may be classified into 

 three kinds, — amoeboid, fusiform, and eleocy tes. To what extent 

 these are distinct in origin I do not know ; but, both in young 

 and mature specimens, they may be clearly distinguished from 

 one another. All three forms may contain brown pigment 

 granules. In Polymnia the fusiform corpuscles^ average about 

 25 fx in length, whilst the amoeboid are of somewhat smaller 

 diameter (figs. 57 and 54). One end of the cell-body of tlie 

 former is sometimes expanded so as to contain a circular body, 

 deeply staining with eosin, in which is placed a granule 

 staining blue with methyl green (fig. 55). 



' Iu Amphitrite the fusiform corpuscles are sometimes drawn out to a 

 considerable length (fig. 44), recalling the statement of Lim Boon Keng (19) 

 that the spindle-shaped cells of Lumbricus may project their ends for great 

 distances. 



