On the Classification of Nemertes and Planarie. 45 
Il. 
The place assigned by Cuvier to the Nemertes and to the Pla- 
nari in his “ Animal Kingdom,” is entirely provisional as ac- 
knowledged by the illustrious naturalist himself. 
emertes are placed in the division of Radiata immedi- 
ately after the Intestina cavitaria. 
Between Nemertes and the intestinal worms of this order there 
are only analogies. The extraordinary length of the body of 
some of them, for instance N. Borlasii (Borlasia anglie), a 
length retninding us of the class of worms, and above all of some 
of the intestinals, such as the tape worm, had prevailed over all 
other considerations. Their aflinities were not acknowledged 
because their organization was unknown. 
At that time the intestinal worms were regarded as Radiata, 
for the reason that their nervous system had not been found, and 
the Nemertes, as well as Planarie, were regarded as intestinal 
worms because all of them reminded us by their forms, of the 
forms of these last. 
When the more recent labors of some zoologists had estab- 
lished beyond any doubt that the intestinal worms belonged to 
the division of Articulata, on account, first, of their having a 
Nervous system, and a nervous system constructed on the plan of 
that group, secondly, by the structure of their body, which is 
Composed of a series of articulations or rings movable upon each 
other, then the Nemertes were carried with the Intestina cavitaria 
Into the division of Articulata where they remained as little known 
a before. It is but of late that they have been made the sub- 
Ject of a special study by a skillful zoologist, Mr. de Quatrefages, 
and J am surprised: that this author has not pointed out the close. 
affinities which they bear to Mollusca. 
Cuvier was well aware of the space which separated Nemertes 
from intestinal worms, inasmuch as he foretold that they would 
ne 
Nees, their structure which as he says “is of an extreme 
softness,” caused him to doubt. Nevertheless it did not, on this 
account, enter into his mind to compare them with Molluses. — 
At that lime, as indeed now, the idea of a mollusc corresponded 
with the idea of a shell-bearing animal, with the form of a body 
zc. or less drawn together into itself, while the lengthening of 
“si involved by analogy the idea of a worm. fe 
mi ape abstracting the form, which is not the characteristic of 
wad Visions, we look at the intimate structure, if we give up . 
the shell as circumscribing the division of Mollusca, we shall 
Nemertes all the principal characters of Molluscs: a 
entirely smooth, covered with a glutinous mucosity ; a 
nervous system reduced toa small number of cephalic 
