MONILIGASTER GRANDIS, A. G. B. 325 
networks, are not present in any region of the body. ‘‘ Latero- 
longitudinal ” vessels are very obvious in the anterior segments, 
from Segment x forwards to Segment v. They are the main 
trunks, in the anterior region of the body, of a system of vessels 
of which the subneural vessel is the main trunk in the pos- 
terior region of the body. This system must be dealt with as 
a whole. 
This system is connected on the one hand with capillary 
networks, and on the other with the hearts of Segment 1x. 
It is, in fact, a venous (using the word in an anatomical sense) 
system for the greater portion of the body. The only capil- 
lary networks with which vessels of this system do not com- 
municate, from which, in fact, they do not carry blood back 
to the hearts, are the capillary networks of the intestinal wall 
from Segment x11 backwards. 
Fach latero-longitudinal trunk may be divided, for purposes 
of description, into three parts, an anterior trunk and a pair 
of posterior trunks. These come together in the anterior 
portion of Segment x, unite into a common trunk which 
passes through Septum 1x-x and opens on each side into the 
heart, or, rather, the neck of the heart of Segment 1x. These 
trunks belong to the cephalised region. The subneural vessel 
exists along the greater portion of the length of the body. It 
is the longitudinal vessel into which open all the vessels 
coming from the capillary networks of the body-wall, septa, 
and nephridia of all the segments posterior to the cephalised 
region. It comes to an end anteriorly in about Segment xiv 
in a very indefinite manner, but all the blood brought for- 
wards by it finds its way into one of the posterior trunks of 
the latero-longitudinal vessel on each side by such vessels as 
a., 6., fig. 27; the exact arrangement is liable to individual 
variation. This strikes one as a very inefficient way of dis- 
posing of so much blood, but the circulation is here, as in all 
veins, comparatively slow, and there can be very little blood- 
pressure; and, besides, the whole circulation in Monili- 
gaster grandis is but feebly carried on in the hinder portion 
of the worm. It is interesting to recall in this connection 
