G8 
SUPPLEMENT 
so much so, that in the living state, they are of a blood-red 
extremely lively. 
In the arenicolse, they are again arbuscular, but they occupy 
the upper part of the root of the thoracic appendages. 
In the amphinomae, and the multidenticulated nereides, 
they arc equally dorsal, and on a more or less considerable 
number of rings of the body, but they are merely pectinated 
and slender; those of the last rings of the body finish by 
even becoming unilobate or cirrhous. 
Finally, none, unless indeed in a rudimentary state, are 
admitted to exist in the aphrodites, in many genera of nereides, 
in the lumbrici, nais, & c. 
The circulatory apparatus of the chetopoda, simply pre- 
sents the vascular portion, without any heart, or true organ 
of impulsion. This vascular part is doubtless composed of 
two orders of vessels, but much less distinct, in any point of 
view, than in the higher animals. 
We may nevertheless consider, as belonging to the venous 
system, a single thick vessel, somewhat flexuous, without 
swellings or dilatations, and which occupies the middle ventral 
line above the nervous system. It is the result, without 
doubt, of the branches which come to it transversely, on each 
side of each ring, in the whole length of the body, except in 
front, where it receives three thick branches, a medial, which 
is placed below the buccal mass, and which is really the con- 
tinuation of the trunk, and two lateral, one on each side, much 
stronger, and which bring back the blood from the buccal mass 
itself by irregular branches, from its muscles, and from the 
skin of the first rings. All this process is very observable in 
the nereis gigas. 
In the species which have the gills attached to the first 
rings of the body, as the serpulae, the amphitritas, and in gene- 
ral all those inhabiting sand, the vessels returning from the 
different ramifications which compose them, render com- 
