4 CTENOPHORES OF THE ATLANTIC COAST OF NORTH AMERICA 
ciliary combs beneath and along the line of which there extends a meri- 
dional longitudinal vessel. 
Two other vessels, the paragastric canals, arise from the funnel- 
cavity in the tentacular plane and extend downward close to and along 
the middle of the broad sides of the stomodzum. 
As this canal-system is complex I have sought to make its arrange- 
ment clear by presenting a diagram in figure 1, which should be con- 
sidered seriously only in so far as it is diagrammatic, and should be 
compared with figs. 4 and 5, which illustrate the conditions seen in 
Pleurobrachia pileus. This diagram attempts to show a perspective view 
of the gastro-vascular cavity. The mouth, m, leads into the laterally 
flattened, slit-like cavity of the stomodeum, st; this in turn leads into 
the laterally flattened infundibulum or funnel, 7, the flat side of which is 
90° apart from the flat side of the stomodeum. The axial funnel-tube, 71, 
leads upward from the funnel to open to the outside through the excre- 
tory pores, ex. The long, narrow ridge of the pole-plate, p, lies in the same 
plane as the stomodeum and 9o° apart from the axis through the funnel 
and tentacles. The funnel, /, gives rise to two tentacular canals, t, two 
paragastric canals, g, and four interradial canals,7. The four interradial 
canals bifurcate and give rise to eight adradial branches, ad, which lead 
to the meridional canals, which are not shown in this figure, but which 
extend along under the combs of cilia. 
In the Cydippide the eight meridional canals and the two paragas- 
tric vessels end blindly near the oral end of the body, but in the higher 
ctenophores of the orders Ganeshidz, Lobate, Cestide, and Beroide their 
oral ends fuse in various ways, forming more or less complete circuits. 
Stages in the development of these fusions are shown in fig. 39, plate 6, 
and figs. 16 and 18, plate 5, and the completed circuits are clearly shown 
in fig. 56, plate 10, which illustrates the condition in Ocyropsis wherein 
there are neither tentacles nor tentacular canals to complicate the figure. 
Figure 2 is a diagram intended to make clear the plan of these fusions 
between the meridional and paragastric canals in the Lobate. For the 
sake of clarity I have left out the auricles, which are four ribbon-like 
expansions of the body on the tentacular sides of the mouth, and around 
the narrow edge of each of which the meridional, subtentacular vessels 
extend. The tentacles and tentacular canals are also omitted in this 
diagram. Vessels on the opposite side of the animal are dotted. The 
diagram shows how the two paragastric canals, g, fork at their oral ends 
and form a ring-canal surrounding the mouth,m, and the four meridional 
subtentacular canals fuse with this ring-canal. The four meridional sub- 
ventral canals, msv, which extend along the outer sides of the oral lobes 
fuse in pairs to form two loop circuits in the lobes, one loop in each lobe. 
This diagram applies only to the Lobate. 
In the Cestidz, on the other hand, the oral forks of the paragastric 
canal of each side of the body unite with the two subtentacular and 
subventral meridional vessels of that side only. Thusin this order there 
is no ring-canal around the mouth. This statement applies also to the 
young of the Beroide, although later the meridional vessels of both sides 
become connected by anastomosing side branches which appear quite 
