68 SUPPLEMENT > 



SO much SO, that in the living state, they are of a blood-red 

 extremely lively. 



In the arenicolas, they are again arbuscular, but they occupy 

 the upper part of the root of the thoracic appendages. 



In the amphinomse, and the multidenticulated nereides, 

 they are 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 amphitritae, and in gene- 

 lal all those inhabiting sand, the vessels returning from the 

 different ramifications which compose them, render com- 



