— 135 — 
subdivided in the dotted substance, and seemed to be entirely broken 
up into slender branches. 
I have observed longitudinal nerve-tubes which seemed to sub- 
divide and be broken up into branches, similar to those longitudinal 
nerve-tubes I have observed in the ventral ganglia of Homarus. 
I have also observed side-branchlets to be given off from longi- 
tudinal nerve-tubes passing along the nerve-cord. 
Finally, I have observed peripheral nerve-tubes springing from 
the dotted substance, being apparently formed by a union of 
slender tubes. 
Peripheral nerve-tubes springing directly from ganghon cells, I 
have, as above mentioned, not been able to trace out, but I have 
been able to trace peripheral nerve-tubes for considerable distances 
through the dotted substance passing frequently over to the other 
side of the ventral nerve-cord, and I believe that they often spring 
directly from ganglion cells. 
From the little we have seen, we may therefore conclude, that 
the constituents of the central mass, or dotted substance, of the 
ventral nerve-cord of Nereis are chiefly the same as those we have 
found in Homarus; the principal constituent is, however, in Nereis 
longitudinally running nerve-tubes, and the other constituents are 
comparatively sparingly present. Masses of a complicated web or 
plaiting of extremely slender tubes, similar to that which is de- 
scribed in the ganglia of Homarus, do not occur in Nereis. 
Upon the whole, the dotted substance of Nereis is very simple 
in its structure, and represents a primary state. 
The suggestion of E. RoHDE ') that the ventral nerve-cord of 
e Polychætes are only developed peripheral nerves because of 
e longitudinally running nerve-tubes, which should indicate the 
nerve-origin, is I think not very well founded. If that is right, the 
ventral nerve-cord of all invertebrated bilaterates which have a nerve- 
cord, must also spring from peripheral nerves only, because in all 
of them there are, according to my investigations, a great many 
longitudinal nerve-tubes, indeed the spinal nerve-cord of the verte- 
brates must also have the same origin. I do not know if this is 
R0HDE's opinion. According to this view the primary state of the 
nerve-system must be a central brain from which nerves only issue. 
Some of these nerves must then at a later stage, by an emigration 
from the brain, or in some other manner, have got ganglion cells. 
1) 1. c. 1 886. 
