ON ANNELIDA. 73 



larly in the Indian, all the other genera have some species in 

 all seas. We may observe, however, that the largest species 

 come to us from the Indian seas. 



It is in general on the shores of the sea, in the midst of 

 thalassiophytes, in the anfractuosities of the madrepores, of 

 rocks, in the sand, and particularly in mud, that the chetopoda 

 are to be found ; and if some s^Decies are more commonly to 

 be met with in the open sea, as, for instance, the amphinomse, 

 named by M. Savigny Pleione vagans, it appears that they 

 may have been drawn along with marine plants by the cur- 

 rents, as is the case with many other animals. 



A great many species are free and wandering, but others li\ e 

 in a tube without being fixed there. 



The position of this tube is rarely horizontal, and when it 

 is vertical, should any chance displace it, the animal torments 

 itself until it has recovered its proper station, as Pallas has 

 frequently proved by experiments on the pectinarise. 



The locomotion of animals of this class is in general rather 

 slow, and may be compared to that of slugs, to a certain ex- 

 tent, though they have a great number of feet, or at least, as 

 we have seen, of appendages that serve for locomotion. This 

 is the case with the species which are most favoured in this 

 respect, such as the nereides. In the aphroditus it is infinitely 

 slower ; and is reduced to a nullity in the serpulse, the amphi- 

 trites, and the sabellaria3 : in fact, they can only rise or sink in 

 the tubes which they inhabit, by their fasciculi or hooked 

 setae. 



The nereides not only creep in a serpentine manner on the 

 surface of solid bodies at the edge of the water, but they often 

 swim very well, either by successive undulations of their 

 bodies, like eels and serpents, or by even agitating their ap- 

 pendages, which serve as oars. 



The chetopoda appear to be for the most part carnassial, and 

 feed upon smaller animals than themselves which come M'ithin 



