— i66 — 
how is an impression, probably, conweyed from a sensitive nerve- 
tube, to a motoric one? As it is chiefly the invertebrated bilaterata 
which have been treated of in this paper, we will also in the present 
inqiury principally confine our remarks to the consideration of their 
nervous system only. 
As is above seen, the sensitive nerve-tube probably subdivides, 
and is broken up into sien der branch es, after its entrance into the 
dotted substance, it is, thus, not very probable, that an irritation of 
such a nerve-tube should be conweyed to one ganglion cell only, 
it would then be necessary that all the branches of a sensitive 
nerve-tube should unite again to form the nervous process of a 
ganglion cell (sensitive ganglion cell). 
According to what is before stated of the combination of the 
ganglion cells it will be obvious that : to be forwarded to a motoric 
cell, the irritation would necessarily after its arrival in the sensitive 
ganglion cell have to return through the same nervous process, to 
pass over through some other branches of the process into the 
nervous process of a motoric cell; arrived in the motoric cell it 
had then to return through the same process and finally pass into 
the centrifugal nerve-tube, to produce the reflex movement. It 
needs no further discussion to see that this would be a highly 
artificial and complicated explanation of the course of an irritation, 
from a centripetal to a centrifugal nerve-tube. For one thing, it is 
not, in my opinion, admissible to assume that all the branches 
arising from the subdivisions of a sensitive tube should re-unite to 
constitute the nervous process of a sensitive ganglion cell; why 
then does the subdivision of the nerve-tube exist, why does not the 
nerve-tube pass undivided to the cell.?* For another thing, I do not 
think it admissible that the same irritation should pass and return 
through the same nervous processes. 
In my opinion, it is a much more probable assumption that 
the irritation does not at all pass through any ganglion cells, but that 
after its arrival in the dotted substance, through subdivisions of 
the centripetal nerve-tube, it is at once carried on, into one or several 
centrifugal nerve-tuhes hy the stender side-branches or fihrillæ joining 
them. How the combination between the branches of the centri- 
petal nerve-tubes and the side-branches of the centrifugal nerve-tubes 
is produced in the dotted substance, can not at present be defined; 
I can not, however, see any objection to the assumption that it 
does exist. 
