440 THOS. H. MONTGOMERY jr., 
branches are given off latero-ventrally from the dorsal duct, and em- 
brace the sides of the intestine (Figs. 18—20, Pl. 38); some extend 
ventrally as far as the lining of parenchym beneath the intestine 
(Int), others reach only half so far. The diameter of these branches 
varies considerably, some being of great thickness and extending over 
a number of sections (sections 6°/, w thick), others being smaller. 
Most of the branches either fork at their free ends, one portion pas- 
sing a short distance forward and the other backward, or else the 
free end without branching bends either forward or backward. The 
free ends of these branches, at least of those which extend down the 
whole side of the intestine, generally diverge away from the intestine. 
The substance of these branches is like that of the dorsal duct. But 
in general they contain many more vacuoles, and in some cases it 
can be positively determined that the most ventral of these vacuoles 
open into the body cavity (here the medio-ventral cavity (Fig. 18, 
left side). The vacuoles and irregular spaces within some of the 
branches appear to form a ramifying canal system, which opens at 
the one end into the body cavity and at the other into the lumen of 
the dorsal duct. None of these parts showed any indications of 
openings into the intestinal lumen. Some of the lacunae, especially 
those which stand in open communication with the body cavity, are 
bounded by a line staining deeply with haematoxylin as in the case 
_ with the lumen of the dorsal duct. In the anterior region where the 
lumen of the main duct is closed, the lumina of the branches are 
likewise closed (Fig. 20). 
As the reconstruction shows (Fig. 12), the branches of the one 
side alternate for the main part with those of the other, and it is 
unusual to find the branches paired. 
It is most remarkable that this organ appears to possess no 
nuclei of its own. Small deep-staining nuclei are found in it (about 
29 in number), but from the close resemblance of these (Par. N 
Fig. 21) to the nuclei of the parasitic organisms found in the lumen 
of the medio-ventral canal, they certainly belong to such parasites 
which have penetrated the wall of the organ. Sometimes such para- 
sitic cells are merely apposed to this organ, sometimes only partially 
imbedded in its branches, sometimes wholly imbedded and in the 
latter case the boundary of the imbedded cell cannot be distinguished 
from the substance of the surrounding organ, though the imbedded 
cell may be recognized as belonging to one of these parasites by the 
peculiarities of its nucleus. 
