RESEARCHES ON THE NERVOUS SYSTEM OF NEMERTINES. 275 
immediately before the anus {Moseley describes such a com- 
missure ill Pelago 7 iemertes) ; and 2nd, the displacement of 
the lateral nerve-cords in the author’s new genus Langia, 
which tend to approach each other on the dorsal side (not 
ventrally as they do in the genera Drepanophorus and 
Oerstedia)i at least in the anterior portion of the body. This 
explanation would restore the homology between the dorsum 
of Vertebrates on the one hand and of Arthropods and 
Annelids on the other, a homology which of late years has 
been put into serious doubt by the researches of Dohrn and 
Semper, whose ingenious suggestions have as yet, however, 
never definitely overcome certain primary objections inherent 
to their views, which correspond as a whole with Geoffroy 
St. Hilaire’s saying that insects are Vertebrates walking on 
their backs. 
After this rapid exposition of the contents of the 
paper, we shall give a somewhat more detailed account 
of certain parts of it. It should here be remarked that the 
nomenclature of the genera and suborders employed is 
that proposed by the author in a former paper,^ in which 
he divides the Nemerteans into three suborders : Palji.one- 
MERTiNi, with the genera Carmella, Cephalotlmx, Polia and 
Valencinia: Schizonemertini, with the genera Linens, 
Borlasia, Cerebratulus and Langia ; Hoplonemertini, with 
the genera Amphiporus, Drepanopliorus , Tetrastemma, Oers- 
tedia, Prosorhochmus, Rnd Nemertes. 
A. The central nervous system, — As such the author 
does not regard the cephalic ganglia only — as was done by 
all his predecessors — but the so-called longitudinal nerves as 
well, on account of the sheath of ganglion cells which unin- 
terruptedly accompanies these trunks from their origin in 
the cephalic lobes down to the extremity of the tail, in all 
the genera without exception. 
Ill the genus Carinella — which appears to be one of the 
more primitive and less difierentiated — the whole central 
nervous system is situated immediately under the epi- 
dermal tissues, outside the muscular body wall (PI. XXIII, 
fig- and the cephalic ganglion takes the form of a simple 
anterior enlargement of the lateral trunks. No distinct 
division into lobes can be detected in transverse sections ; the 
ventral commissure is very broad, the dorsal commissure ex- 
ceedingly thin; through the ring thus formed the proboscis 
and its sheath passes (PI. XXIII, fig. 2). The mouth opens 
behind and under the ganglion. The fibrous nerve-sub- 
' The Genera of European Nemerteans Critically llevised,” ‘ Notes 
from the Leyden Museum,’ vol. i, p. 193 . 
