— 140 — 
neuroglia-fibrillæ resemble in their aspect the fine nerve-fibrillæ, so 
very much, that I am not at present in a position to point out any 
distinct difference between them.^) 
As to an interfibrillar substance, which many authors describe, it 
may be stated that, in fresh preparations, I have occasionally observed 
hyaline pearls adhering to the sides of the fibrillæ (vide fig. 85, h). In 
my opinion these pearls do not, however, spring from an interfibrillar 
substance, but are pearls of hyaloplasm, springing from destroyed 
nerve-tubes. 
The origin of the constitiients, forming the dotted substance, we 
will find to be quite correspondent to what is found in Homams. 
All the nervous processes of the ganglion cells are, as already 
mentioned, directed towards, and penetrate into, the dotted substance. 
As in Homams, and the other animals examined, it may be 
seen that some nervous processes (vide fig. 73, h, w"; 74, a, c, d, /; 75 ; 
76; 78; 82,(2; 83,(2) retain their individuality, in their course through 
the dotted subsance, and as far as they can be traced are not seen 
to subdivide; at intervals, however, they give off some few fine side- 
hranchlets, at the origin of which small varicose thickenings frequently 
occur (fig. 74, a, f] fig. 75, 76). 
Other nervous processes (vide fig. 73, /^'; fig. 74, h, i] fig. 77) 
lose their individuality; they subdivide and are hroTcen up into stender 
nerve- fibrillæ. 
We have thus two types of nervous processes, like what is 
found in Homarus etc. 
As to the course and termination of the many longitudinal 
nerve-tubes, which form such a material part of the dotted sub- 
stance of the pedal nerve-cord, little can be said at present. In 
some of them I have observed side-branchlets to be given off, in 
others I have occasionally seen subdivisions ; but upon the whole my 
present methods of investigation have been insufficient to trace out 
these very slender structures. A great many of them are, however, 
easily seen to pass into peripheral nerves, forming peripheral nerve- 
tubes. 
As to the origin of the peripheral nerve-tubes, my investigations 
are also in that respect very imperfect. I have observed nerve-tubes 
which, probably, come directly from ganglion cells, as they could be 
traced for long distances in their course through the dotted substance 
without subdividing, only giving off some few side-branchlets; 
^) Vide also my description of the nerve-tubes of the MoUusca p. 94 — 96. 
