On the Classification of Nemertes and Planarie. 49 
surface of their body; that they are Gasteropods, there can be 
no doubt. Do we not see them, as well as Pulmonata, Nudi- 
branchiata and others, creeping along the walls of a basin and 
when near the surface of the water, reversing their position and 
walking in that manner with the same facility ?, Do we not witness 
the same undulatory contractions in that foot? Therefore were 
not Baer and Dugés guided aright when they compared the infe- 
rior surface of the body of Planarie to the foot of Gasteropods ? 
am not aware that any of the Planarice I have studied moves 
with the same facility on the back as on the belly as Mr. de 
Quatrefages states. Whenever I placed them in that position I 
always saw them changing it as quickly as possible. Besides in 
most cases I have seen the upper surface differing widely from 
the inferior one. 
ior tentacles of Eolidicera and in the same place as in these last. 
ee There exist then in the marine Planarie# one group which re- 
Minds us of Doris, another of Eolis, and still another group in- 
termediate between Eolis and Planaria proper which lead to the 
freshwater species. 
This shows that it is near Nudibranchiata that Planarie will 
find a natural place, and on several accounts we should be tempt- 
a Strongly defined as this latter, and representing merely a variation 
- » Mthe thought of the Creator. 
_For, in Nudibranchiata we find a number of types all as much 
diversified. These are: Doridians, Folidians, then Canthop- 
sis analogous to Procerodes which leads to the Acteonians, then 
finally the genera Pelta and Chalidis which constitute another 
hind’ almost Planarian, deprived of external appendages of any 
There exists a strikin llelism between the zoological forms 
of these two families. : = ee : 
7. lewed in the light of their organization nothing is more alike. 
he nervous and digestive systems scarcely differ. I have already. 
Spok he first. With regard to the second I shall recall the 
is ramified in Nudibranchiata as in Planarie; the 
ns being diversified according to the groups. 
is 7 
