MONILIGASTER GRANDIS, A. G. B. 383 
and outer seta lines. The position of the septum bounding anteriorly the 
segment which contains this nephridium, at the place where the nephrostomial 
duct perforates it, is shown at sepé., so that the vesicle and adjoining portions 
of the nephridium are supposed to have been turned forwards. ‘The greater 
part of the gland is shown in optical section; but at certain places, left un- 
shaded, a view nearer the surface is taken. This will be intelligible on a 
comparison with the text. s¢. Nephrostome. sf. a. Nephrostomial duct. 
This duct joins the rest of the gland at a. The duct which passes from a to 
4 is shown in three places in the surface views, and marked “ad.” The duct 
which passes from 4 to c is shown in three places, and marked “dc.” The 
duct passing from ¢ to dis marked “cd.” The duct passing from d to e is 
marked “de.” The duct passing from e to fis marked “ef” The duct 
passing from / to g is marked “fy.” The vesicle duct passing from g to 4, the 
point where it opens into the vesicle is marked “gi.” ves. Vesicle; the 
muscles shown in a portion of its walls only. y. Sphincter muscle. ez. apt. 
Place where the excretory duct penetrates to the body-wall to pass to the 
nephridiopore. 
Fig. 43.—A nephrostome, fixed and stained, showing forty-five marginal 
cells, two nuclei of central cells, and at the margin the flattened nuclei of 
celomic epithelium cells. 
Fic. 44.—Section through a nephrostome, with a portion of the duct, 
showing a nucleus, c, of a central cell and a nucleus, m, of a marginal cell. 
Fie. 45.—Portion of a nephridial ductule with undulating bundles. 
Fic. 46.—Surface view of a portion of the nephridium in the region “ ad,” 
drawn from a freshly mounted preparation. 
Fies. 47 and 48.—Transverse sections of the ventral nerve-cord. Fig. 47, 
from an interganglionic region; Fig. 48, passing through a ganglion and 
through the origin of one of the nerve branches on one side. The two figures 
drawn with the camera lucida to the same scale. ep. Celomic epithelium. 
ce. t. Connective-tissue sheath. s. Space left owing to the contraction of 4., 
the hyaline sheath, in which are embedded the muscles, musc. g.f. Giant 
fibre. 2. 7 Nerve fibres. g/. Neuroglia. gang. Ganglion cell. v. Blood 
capillaries. 
PLATE 28. 
Moniligaster grandis, 
Fic. 49.—View of a dissection to show the bands of muscle, ., which are 
connected with the body-wall in the neighbourhood of the male pore (? copu- 
latory muscles). JV.c. Nerve-cord, with the three nerves, 1, 2, 3, of Segment x 
and the first nerve of Segment x1. Septum 9/10 is turned forward, and 
Septum 10/11, to which is also attached Septum 11/12 (not shown) is turned 
