ON ANNELIDA. 
107 
tlier by means of numerous cellular frcena, which are carried 
from one to the other, forming numerous transverse cells. 
The termination of the intestine is made, as has been al- 
ready mentioned, altogether at the posterior extremity of the 
body. It is usually very wide and transverse. 
No liver, properly so called, has been distinguished round 
any part of the intestinal canal of the nereides, but the sali- 
vary glands have been found to be particularly distinct, at 
least in the unidentated species. 
The portion of the exterior envelope, modified so as to be 
converted into an organ of respiration, is constantly external 
in the nereides, and consequently constitutes gills, but those 
gills are not always perfectly distinct from the tentacular 
cirri of the appendages of the rings, in which case it is pro- 
bable that the latter take the place of them. In the multi- 
dentated nereides there are some very distinct, and which are 
often even more or less pinnated. In the unidentated species 
the lateral cephalic tentacula may doubtless be regarded as 
gills, as well as the little cirrous tongues, which are found 
underneath the superior and inferior cirri. Finally, in the 
species with proboscis, it is very rare that there is any thing 
else but simple tentacular cirri, sometimes, it is true, aug- 
mented at the superior part with sorts of cirri compressed 
into little leaves, which may also be regarded as respiratory 
organs, but from no proof except analogy of position. 
The circulation of the nereides appears to be extremely 
simple ; and the blood is constantly of a fine red colour, com- 
parable to that of the arterial blood of vertebrated animals, 
with warm blood, and that in the whole vascular system. 
The apparatus of decomposition in these animals is still 
less known than that of composition. The cutaneous exha- 
lation is sometimes sufficiently abundant, since certain 
species can form from it a sheath, or at least line their 
