* 
ee =n s ; 
50 On the Classification of Nemertes and Planarie. a 
prise 
- Jong, they assume a othe analogous to a group of the division of 
Articulata which attract them but to which they do not belong. 
pro- 
The organs of generation do not differ much more. Nudi- 
branchiata are androgynous like Planarie. Mire fecundation 
takes place by mutual fecundation as is the case ulmonata. 
But in Planarize we have cases where an individual fecundates 
itself, the hermaphroditism being here complete 
N.. 
It still He for me to make some general remarks upon Ne- 
mertes and Pla 
Mr. de inalietiges tells us himself, “neither Nemertes nor 
Planarie have externally a resistant and tough layer, similar to 
that which is found with Annelids, for example, or even with 
Rotatoria.”* 
We have then two groups of Gasteropodous molluscs parallel 
with two groups of annulated Articulata; the group of Planarie 
reminding us of Helminthes, and the group of Nemertes remind- 
ing us of the Hirudines. 
“At the extremes of these two groups, at the bottom of the two 
rial property. As examples we have: 
In Molluscs,—the Nemertes which elongate and become worm- 
like; the Planarize etal remain shorter but pressed down, spread 
out, flattened in thin leav 
In Articulata,—the ere of Helminthes in general, the flat- 
tening of their body i in T'rematodes in which the articulation 0 
the body vanishes, analogous to Planaric ;—the softness still of 
the Leeches with a distinct articulated structure, being parallel 
with Nemertes 
These groups do not oppose each other in an exact parallelism, 
for Nemertes which form a low type of Gasteropods are opposed 
to the Leeches of a higher grade of worms, and Planariz ahigher 
rade among Gasteropods are opposed to Trematodes a lower «~~ 
type among worms. In this manner: . 
Hirudines, Planariz, 3 
Trematodes, a Nemertes, ee 
In the elongation of the Bédy of Nemertes there is nothing to 
sur us. Placed at the bottom of the class to which they be- 
a See 
Now when a Mollusc, whose body is elongated beyond all 
* Ann. Sc, Nat., 3d series, vol. iv, 1845. 
