ON ANNELIDA. 
115 
In the passage of the intestinal canal, the muscular fibres 
which pass from one ring of the body to another, attaching 
themselves to the interval, form sorts of diaphragms, which 
proceed to terminate at the parietes of the intestine. No 
author speaks of the liver, properly so called. Some, how- 
ever, have considered as holding its place, a thick flexuous 
vessel, which predominates all along the inferior face of the 
intestinal canal. But this is probably an erroneous opinion, 
this vessel being more likely to be a mesenteric vein. The 
apparatus of the circulation of the lumbrici appears to be 
very simple. From all the parts of the exterior envelope, 
and from the intestinal canal, springs a very close net-work 
of small veins, which unite in a single thick trunk, situated in 
the medial line of the ventral face. This trunk, when ar- 
rived near the head, ascends by five pair of lateral canals, 
to the dorsal surface of the body. These canals soon unite in 
a very long heart, occupying all the middle line of the back, 
broader in front, and growing more narrow in proportion as 
it goes backwards. The heart may then very well be con- 
sidered as an aortal artery, from which, subsequently issue 
the divisions which repair into the different parts of the body. 
Its motions of systole and diastole are very perceptible. 
From this distribution of the circulatory apparatus, it is ex- 
tremely probable that there is no special organ of respiration, 
and that the entire skin is modified for this purpose. There 
are, however, many authors who regard as sorts of lungs, the 
little follicles, to which the dorsal pores conduct, as the same 
has been supposed with regard to the leeches. The organs 
of generation appear to have sufficient relations with those of 
the same animals. Like them, the two sexes exist in the 
same individual, and the apparatus are situated towards the 
anterior third of the body. They are composed, behind, of a 
double series of yellowish pores, situated above the stomach, 
into which repair a great number of blood-vessels, and in front. 
