RESEARCHES ON THE NERVOUS SYSTEM OF NEMERTINES. 281 
especially because here the circulation is more perfected and 
the blood-corpuscles are haemoglobinous themselves,, the 
nerve-tissue, at the same time, losing its deep-red tinge. 
Only he adds that, not being able to detect any sensory epi- 
thelium in these organs, he is provisionally inclined to doubt 
whether, after having lost their primary respiratory signifi- 
cance, they ever become secondarily modified into a sense- 
organ in the higher differentiated forms. 
c. Histology of the neroe-centres, peripheral nerves^ ^c. 
— Respecting the further histological and anatomical results, 
we may rapidly note the following : — The ganglion cells in 
the brain, in all genera above Garinella and Cephalotrix, 
surround the central mass of nerve-fibre on all sides. This 
fibrous skeleton” of the central apparatus is figured for the 
ScHizoNEMERTiNi ill PI. XXIII, fig. 1 ; the right dorsal 
lobe is supposed to have been removed in order to show the 
ventral one. The fibrous nerve-substance is indicated by a 
paler, the cellular by a darker tint. The general shape and 
distribution of this fibrous nucleus of the brain may be 
gathered from the figure ; it is also continued into the posterior 
brain lobe. 
A very thin homogeneous layer separates the fibrous from 
the cellular nerve-substance ; the processes of the nerve- 
cells (very few multipolar, the majority apparently unipolar) 
are seen to perforate this homogeneous layer, and to pene- 
trate into the central fibrous substance. The larger nerves 
for the eyes and the tip of the snout, those for the proboscis, 
and those for the oesophagus, are seen, as well on compression 
as in sections, to take their origin in this central fibrous 
nerve-skeleton. The two latter sets of nerves are'lfor the 
first time correctly described by the author. For Carinella 
he succeeded in demonstrating the direct passage of strong 
nerves, leaving the brain close to the ventral commissure 
into the proboscis, where they continue their course longi- 
tudinally between the muscular and the cellular coating. 
Identical nerves were clearly made out in certain Schizo- 
NEMERTiNi, and for some of the Hoplonemertini von 
KenneV s suggestion that MeIntosW s beaded layer” in the 
proboscis of this group is of a nervous nature was fully con- 
firmed, and at the same time the distribution of delicate and 
numerous nerve-twigs going to the papillae of this proboscis 
was made out. 
Next to this proboscidian nerve another strong nerve leaves 
the brain, springing from the posterior portion of the inferior 
This pair of nerves is present in all Nemerteans, and 
lobes. 
is intended for the anterior portion of the alimentary canal.. 
