^110. THE HELMINTHES. 115 



CHAPTER VI. 



CIRCULATORY SYSTEM. 



§ no. 



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 lemnisci, 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 Eckitiorhynckus, 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- 

 chyma of the proboscis.*^' 



In many,'^' the lemuisci are surrounded by muscular fibres, which, con- 

 verging to the posterior extremity of these oi-gans, 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- norhynchus claviceps, they are longer than the 



mintholojjists for a digestive canal,"lias been fig- body, and lie coiled in its cavity. In Echino- 



ured by Westrwmi (De Helminth Acanthocephalis rhijnchus gibbosus, hystrix. and strumosus. 



Tab. II. fig. 10, IH. fig. 10, 12, 21), and Burow they are discoid and very short. 



(Echinorhynchi strumosf Anat. ISotJ, fig. 1, S). •') ErMnorhynclms am^ustatus, haeruca, poly- 



The movements of the nutritive liquid may be morphus, proteus, and gibbosus. As a wide 



distinctly seen by placing these animals alive and e.xception. the principal canal occupies the median 



undilated ;is natural under the microscope. One line of the lemniscii, and sends off laterally small 



will then be quickly convinced that the circulation branches, with Ecliinnrhynchus gigas. Here 



is due to the general movements of the body. If and there its course is broken by oval, voluminoup, 



Echinorhynchus is placed in much water, the transparent and apparently vesicular bodies ; see 



absorption distends not only the body, but the fVestrumb loc. cit. Tab. II. fig. 7. Similar bodies 



canals of the vascular system are sj filled that the in the leniTiisci and subcutaneous parenchyma, are 



subcutaneous parenchyma is swoUan, and the found with Echinorhynchus claviceps ; see Miil- 



Bkin is raised here and there into vesicles. ler, Zool. Dauica. Tab. LXI. fig- 3. These bodies 



'i With Echinorhynchus angastatus, acus, are, moreover, regular neither as t) their number 



fusiformis, proteus, and polymorphus, the two nor position, and I have not learned their nature, 



lemnisci have a riband-like form. In Echino- * Echinorhynchus acus, angustatus, fusifor- 



rhynchus gigas, they are very long ; and in Echi- mis, and proteus. 



