$110. THE HELMINTHES. 115 
CHAPTER VI. 
CIRCULATORY SYSTEM. 
§ 110. 
Most of these animals have a vascular system. The circulating liquid 
is usually wholly colorless, and often contains vesicular or granular cor- 
puscles, which are difficult to perceive from their delicacy and transparency. 
The circulation is due to the general contractions of the body or of the 
walls of the vessels. 
In the Acanthocephali, the vessels have no proper walls, but are spread 
out, as has already been said (§ 106), in the subcutaneous parenchyma, 
There are two larger, lateral canals, which pass from the neck to the caudal 
extremity, sending off laterally numerous small canals, which anastomose 
with each other. A similar net-work is found in the proboscis through its 
whole length.” These two canals connect also with the demmnisci, upon 
each side of the neck. These last, of which there are always two upon the 
sides of the proboscis, passing from the neck to the cavity of the body, are 
usually riband-like, and composed of a finely-granulated parenchyma, 
which, like the cutaneous one, has a system of vascular canals. 
In most species of Echinorhynchus, this system consists-of a main canal 
upon the border of the lemniscus, from which are sent off inwardly, nu- 
merous small branches. These last form the net-work which fills the paren- 
cchyma of the proboscis. 
n many, the lemnisci are surrounded by muscular fibres, which, con- 
verging to the posterior uxtremity of these organs, form two short muscles, 
which, in their turn, are blended with those passing obliquely to the pro- 
boscideal sheath. The point of junction is at a short distance from the 
place where they are detached from the subcutaneous muscular layer. 
Each lemniscus is constricted into a narrow neck at its base, which passes 
into the skin at the base of the proboscis. The junction of the cutaneous 
with the lemniscian vascular system occurs at this point, as is indicated by 
the contained liquid passing backwards and forwards between the two from 
1 This vascular system, taken by many Hel- 
aminthologists for a digestive canal, has been fig- 
ured by Westrumb (De Helminth Acanthocephalis 
Tab. II. fig. 10, IIL. fig. 10, 12, 21), and Burow 
(Echinorhynchi strumosi Anat. 1836, fig. 1, 8). 
The movements of the nutritive liquid may be 
distinctly seen by placing these animals alive and 
undilated as natural under the microscope. One 
will then be quickly convinced that the circulation 
is due to the general movements of the body. If 
Echinorhynchus is placed in much water, the 
absorption distends not only the body, but the 
canals of the vascular system are so filled that the 
subcutaneous parenchyma is swollen, and the 
skin is raised here and there into vesicles. 
2 With Echinorhynchus angustatus, acus, 
Susiformis, proteus, and polymorphus, the two 
femnisci have a riband-like form. In Echino- 
wrhynchus gigas, they are very long ; and in Echi- 
norhynchus claviceps, they are longer than the 
body, and lie coiled in its cavity. In Echino- 
rhynchus gibbosus, hystrix. and strumosus, 
they are discoid and very short. 
83 Echinorhynchus angustatus, haeruca, poly- 
morphus, proteus, and gibbosus. As a wide 
exception, the principal canal occupies the median 
line of the lemniscii, and sends off laterally small 
branches, with Echinorhynchus gigas. Here 
and there its course is broken by oval, voluminoua, 
transparent and apparently vesicular bodies ; see 
Westrumb loc. cit. Tab. II. fig. 7. Similar bodies 
in the lemnisci and subcutaneous parenchyma, are 
found with Echinorhynch laviceps ; see Mil- 
ler, Zool. Danica. Tab. LXI. fig. 3. These bodies 
are, moreover, regular neither as to their number 
nor position, and I have not learned their nature. 
4 Echinorhynchus acus, angustatus, fusifor= 
mis, and proteus. 
