388 MR. R. OWEN’S REMARKS ON THE ENTOZOA. 
The difficulty of assigning a distinctive character to the Entozoa, which Rudolphi 
imagined he had overcome in the ‘ Historia Entozoorum’ by denying them a nervous 
system, and so distinguishing them from the Annulate Worms, he justly allows in his 
subsequent work, the ‘ Synopsis Entozoorum’!, to have returned in its full force, and 
proposes therefore to separate the Nematoidea from the other orders of Entozoa, and to 
join them with the Annulata (Annelides, Cuvier), in which class of Worms he thinks they 
should form a distinct family. The remaining Entozoa (the Vers Intestinaux Parenchy- 
mateux of Cuvier) Rudolphi leaves among the Radiata or Zoophyta, a division of animals 
which he justly terms ‘ regnum chaoticum.’ 
With respect to the affinity of the Nematoidea to the Red-blooded Worms, the im- 
portant differences which the presence in the latter class of distinct respiratory organs 
and of vessels circulating red blood present, obviously forbid the junction proposed by 
Rudolphi, at least in any attempt at a natural arrangement. While the absence of 
ganglions on the nervous chords, which supply the body in the Nematoidea with the 
motive and sensitive endowments, bespeaks a difference of still greater importance. 
As the Nematoidea, or Vers Intestinaux Cavitaires, differ from the Vers Parenchymateux 
in the presence of a distinct nervous system, as widely on the one hand as they do from 
the Annelida in the form of that system on the other, I have been induced to join them 
with those other classes of the Radiata of Cuvier which, while they are distinguished 
from the rest of that Division of the Animal Kingdom by the undoubted presence of 
nerves, agree with the Nematoidea in manifesting those organs in the form of simple, 
ungangliated, disconnected cords. 
In attempting therefore a more natural arrangement of the Entozoa, I have been led 
to propose a division of the Radiata of the ‘ Régne Animal’ into two groups, founded 
principally on the two conditions which the nervous system presents, the molecular and 
the filiform. The necessity of such a dismemberment appears to have been felt by every 
naturalist who has considered the natural affinities of the classes which are included in 
the lowest division of Cuvier’s system. His Radiata, indeed, embrace animals which 
differ widely from one another, not only in the condition of the nervous but of many 
other important systems of their organization ; and, as the division now stands, an ana- 
tomist is unable to predicate a community of structure in either the locomotive, ex- 
cretive, digestive, sensitive, or generative systems of the various classes which it em- 
braces. 
The learned entomologist Mr. W. 8S. MacLeay has proposed, in the sketch of the 
natural affinities which he has given in the second volume of the ‘ Hore Entomologice’, 
to limit the term Radiata to the Echinodermata and Acalepha of Cuvier, which alone, as 
he justly observes, strictly present the radiated form of the body, and to form a distinct 
division of the animal kingdom, to include the Infusoria, Cuv., Polypi, Cuv., and Paren- 
chymatous Entozoa under the term Acrita, while the Intestinaua Cavitaires are trans- 
ferred to the Annulose or Articulate division of the animal kingdom ; they are not, in- 
1p. 572. 
