On the Classification of Nemertes and Planaria. SL 
portion, and obliged sometimes to move by the contraction of 
transverse muscular fibres, accelerates its progress, then .we see 
that Mollusc assuming certain transverse, irregular and unequal 
folds,—shadows of articulations which in reality do not exist. 
At the bottom of the division of Articulata we observe similar 
facts. The Trematodes lose insensibly that elongated form of 
the body which constitutes the prominent character of the worms ; 
they are flattened, spread out, meanwhile the articulation of the 
H body, the characteristic of their type, vanishes completely,—thus 
h foreshadowing the type of Planarie. ; 
fe lhe position and number of eye-specks in Nemertes and Pla- 
nari indicate also a greater resemblance to the same organs in 
Molluscs than to those of Annelids. When eyes exist in Anne- 
lids, they are arranged in pairs on both sides of each articulation 
or else form a crown on one of the anterior rings. In Planarize 
we find the eye-specks irregularly grouped on the upper surface 
hear the anterior region of the body. The same arrangement is 
5: observed in Nemertes. This arrangement forcibly reminds us of 
what we see in Gasteropods. In Planariz alone they are more 
humerous and distributed with less constancy, a fact which is ac- 
counted for by the lower position of that family in the class. 
™ he habits of Nemertes and Planari speak rather in favor of 
z Molluses than worms. Most of them live concealed under stones 
Which is the case with many Molluscs, while I do not know 
any which lives within a tube constructed like those of worms. 
e embryonic development of both Nemertes and Planarize 
Rees takes place according to the laws we witness among Gasteropods. 
& The larval condition of both Gasteropods and Planarie is very 
Similar, 
It is plain enough, Nemertes and Planarie are only analogous 
i to Articulata; by their affinities they are Molluscs. The divis- 
ton of Articulata hence appears to us as a type more natural and 
Le Tational, as well as that of Mollusca; this latter including all an- 
at: nt which are soft, slimy and flabby, whatever may be t eir 
» 
be * % * * * * 
i The Rhabdoceelee or freshwater Planarie will be the connecting 
ink by which the Nemertes approach Planariz proper, as mem- 
ne of the same group. We say of them that they are the 
reshwater representatives of both Nemertes and Planarie. And 
2. ere the transition: the group, Rhabdoceele, which is 
in fresh waters, while the other two groups which 
t together are scarcely found beyond the boundaries 
If some of them ascend the rivers it is within the 
ere the water still retains a part of its marine character. 
 Tepeat, lives 
_ they connec 
Bd 
'nguished at once from Planarie and Nemertes, this group, I 
