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 membrane (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 be readily recognised, placed at 
fairly regular intervals from each other, but the cell bodies are 
not distinct in my preparations. As the heart-bladder decreases 
in size posteriorly the cells of the dorsal strand unite with 
processes from the irregular endothelial cells of the ventral wall, 
and eventually the posterior part of the cavity is filled up as in Ft. 
minnta by a mass of tissue denser than that of the anterior end 
(fig. 9, h.), 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, 
(flm.). 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 epithelium, 
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 very narrow 
interval. These muscular fibres in the glomerulus of this species 
