18 ON A NEW SPECIES OF ENTEROPNEUSTA, 



cells do not form in this species, so far as I have observed, a 

 definite layer, but are irregularly disposed (figs. 4 and 5), and 

 very frequently some of them are of an elongated form with one 

 end attached to the heart-bladder wall. The portion of the 

 anterior cell mass above the cavity continues as a narrow strand 

 occupying the apex of the cavity of the heart-bladder, and limited 

 from it by a very tender meml^rane (fig. 5). This dorsal strand 

 of tissue passes on either side into the flattened endothelium 

 which lines the lateral walls of the heart-bladder. The rounded 

 nuclei of this endothelium can he readily recognised, placed at 

 fairly regular intervals from each other, but the cell bodies are 

 not distinct in my prejDarations. As the heart-bladder decreases 

 in size posteriorly the cells of the dorsal strand unite wdth 

 processes from the irregular endothelial cells of the ventral wall, 

 and eventually the posterior part of the cavity is filled up as in Pt. 

 minuta by a mass of tissue denser than that of the anterior end 

 (fig. 9, A.), and through which there pass between the lateral 

 walls of the heart-bladder fine transverse fibres which Spengel 

 regards as muscular. 



Yellow granules may sometimes be observed in the cellular 

 tissue in the heart-bladder. 



Glomerulus : The glomerulus will be dealt with in connection 

 with the vascular system, and I need only mention here one point 

 in connection with it. Lying on the splanchnic epithelium and 

 internal to it between the glomerulus vessels I have observed, in 

 some individuals of this species though not in all the series I 

 have examined, some bundles of parallel muscular fibres (fig. 6, 

 ((hn.). They very often have the appearance of being inserted 

 into the tender membrane forming the walls of the vessels of the 

 net at the periphery of the glomerulus. The fibres also frequently 

 project beyond the outer surface of the splanchnic ei3ithelium, 

 and readily give one the impression that they were during life 

 continuous with similar bundles which lie at the inner edges of 

 the radial masses bounding the space surrounding the proboscis 

 organs, and from which they are separated only by a A'ery narr<)\\- 

 interval. These muscular fibres in the glomerulus of this species 



