HEART-BODY, ETC., OF CEIiTATN POLYCniETA. 287 



states that in Coppingeria the cellular structure is only repre- 

 sented by nuclei. 



In Siphonostoma, Stylaroides, and Trophonia there is no 

 such development of the coelomic epithelium as that in Cir- 

 ratulidse. If excretory products be passed through the 

 heart-wall, as suggested in the case of that group, they would 

 be received directly by the coelomic fluid or its cellular ele- 

 ments. The latter consist in Siphonostoma of colourless cells, 

 containing large nuclei, in some cases with very little sur- 

 rounding protoplasm, in others, however, with a considerable 

 cell body of a pointed oval shape (fig. 37) , staining strongly with 

 eosin, usually somewhat vacuolated, and containing one or two 

 small dark spherules. In Trophonia, besides small vacuolated 

 fusiform cells (fig. 40), which are often drawn out to a fine 

 point at one end, as in the corpuscles described by Good- 

 rich in Enchytrseus hortensis (14, p. 56), where the 

 processes in an early stage of the corpuscles attached them to 

 the walls of the coelom ; there are also somewhat larger cells 

 (fig. 41) with nuclei of the same size, but with their protoplasm^ 

 in specimens rapidly fixed, entirely drawn out into broad 

 flattened projections which radiate from the nucleus like the 

 petals of a flower. In both kinds of corpuscles, when exa- 

 mined fresh, vacuoles and yellow granules are observed, the 

 latter being sometimes as large as the chitinous granules in 

 the ordinary corpuscles of Capitellidse, and with a similar con- 

 centric marking.^ 



1 Pkoblematical Bodies constantly present in the Ccelomic Fluid 

 OF Siphonostoma and Trophonia. 



Jourdan (17, p. 33) describes in Siphonostoma crystalline calculi con- 

 tained in the mesenteries, especially that of the stomach. I find similar 

 structures, with their cellular envelope around them, constantly present, 

 floating freely in the coelom (figs. 38 and 39). The calculi are usually spherical, 

 and tend to split into segments radially. They are pale green in colour. 



In Trophonia bodies occur in the coelomic fluid which are possibly of a 

 similar nature. They are colourless rods, usually shaped somewhat in the 

 form of a figure of 8, and are enclosed in an envelope formed of a few cells, 

 in the substance of which are some globules of fat (fig. 43). In the centre of 

 the rod is an elongated dark streak. The whole structure has a striking 



