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208 CLASS VI. 
the same time, added to it the Entozoa*. Some years afterwards 
CuVIER discovered that many of these animals have red-coloured 
blood, and thought that a name implying this was justifiable (vers 
& sang rouge), whilst LAMARCK, on account of the rings into which 
their body is divided, named them Annelides. 
It was necessary to premise these historical notices in order to 
make it clear why we have given to this class of animals the name 
“Ringed Worms;” and, notwithstanding, include in it animals 
whose body is not divided into rings. The name may be defended 
by similar instances from other classes of animals, where names do 
not always suit all the individuals in them. But, further, we 
prefer this name to that of “‘ Worms,” because this last is too 
indeterminate, and, as has been alleged above, has a double meaning. 
One of the best writers on the Annulata is O. F. MUELLER, to 
whom the whole of Zoology is indebted for distinguished services. 
The immortal PAuias, also, described many rmged worms, and 
investigated them anatomically. In the present century they have 
been especially investigated by Saviany, Mitne Epwarps, GRUBE 
and OERSTED. EHRENBERG has placed some of these worms, 
on account of the vibratile cilia with which their integument is 
beset, in a separate class, under the name Turbellaria. But, besides 
that we think too great a multiplicity of classes is to be avoided, 
some of these Turbellaria approach far too nearly to other natural 
divisions of the Annulata to allow us to place them in a distinct 
class of the animal kingdom ®. 
Cuvier and LAmARrcK placed the Annulata higher in the animal 
kingdom than the rest of the articulates ; above the Crustaceans. It 
is true that the last-named Zoologist considered the Crustaceans to be 
the more highly organised, but believing that the Annulata ought to 
stand above the Insects, and that it was inexpedient to break the con- 
nected series formed by the Insects, Arachnoids, and Crustaceans, 
1 Tableau élément. de [ Hist. nat. des Animaux, 1798, p. 624; Leg. d’Anat. com- 
parée tl. tvieme Tableau. LAMARCK adopted the same class in his Systéme des Anim. 
sans vertébres, 1801, p. 315. 
2 The class of the Acalephe for instance, the order of the hemiptera, a name which 
is properly applicable to the division of the heteroptera alone. 
3 In the following general view of the internal structure of this class we shall 
especially fix our regards on those animals which indicate most clearly the articulate 
type; for the rest we refer to the special notices in the Systematic Arrangement. 
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