ON ANNELIDA. 107 



ther 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 



