ON ANNELIDA. 95 



years the systematic writers adopted this genus, such as it is 

 in Gmehn, almost without making any other change than 

 adding a very small number of species. This may be easily 

 seen in Bruguieres' " Tableau des Vers," in the Encyclope- 

 dic Methodique, Blumenbach's Manual of Natural History, 

 that of the Baron Cuvier, the first edition of Invertebrated 

 Animals, by M. de Lamarck, and even in M. Bosc's Treatise 

 of Worms, although he indicates some new species. In the 

 first mentioned work, however, we find a new established 

 genus upon a species equally new, and the observation that 

 the three sections of Linna3us and Gmelin should form so 

 many distinct genera, when the mouth of the animals com- 

 posing them should be better known. M. Oken also esta- 

 blished a small section in this genus, but without any new 

 observations. The naturalists of our country, in the mean 

 time, and among others MM. Donovan and Leach, made 

 known some species of Nereides not before observed. The 

 nature of the labours of M. de Blainville also led him to 

 endeavour to throw some light on this great genus, by care- 

 fully studying the small number of species which he could 

 procure. It was thus in considering the disposition or com- 

 position of the appendages of these animals, that he was led 

 to this result, of some importance to the philosophy of the 

 science, that in the animals articulated externally, to which 

 he has given the typical name oi entomozoaria, o\ entomozoa, 

 each ring of the body in its complete state is provided with 

 appendages, formed of three parts, one respiratory, or bran- 

 chial, the other locomotive, and the third sensitive ; that all 

 the rings are not necessarily provided with these parts of the 

 appendage ; that it may have three, two only, or one, or 

 there may be none whatever in some of the lowest species, or 

 in some parts of the body of an animal modified by some 

 other cause. From this point the transition was easy to 

 show how in the Nereides the general respiratory and loco- 



