— 144 — 
Neuroglia-nuclei are scattered through the dotted substance of 
the Ascidia ; they distinguish themselves from the nuclei of the before 
mentioned ganglion cells, also occurring in the dotted substance, 
by a darker staining, a more oblong form, and a more granular 
appearance ; they are also generally of a smaller size than the latter. 
As before said, neuroglia-fibres are very often seen in connection 
with these neuroglia-nuclei. Sometimes neuroglia-nuclei are seen 
adhering to the nervous processes issuing from the ganglion cells 
(vide fig. 87). 
Su mm a ry. 
If we now gather together the results of our previous researches 
on the structure of the dotted substance, and if we assume them 
to be applicable to the dotted substance of all invertebrated bi- 
iaterates — which we may probably do, seeing the correspondence 
between the principal characteritics in the structure of the various 
groups investigated — we may give the following summary of our 
investigations : 
The dotted substance of all invertebrated bilaterates consists 
chiefly of nerve-tubes, and primitive-tubes (and nerve-fibrillæ which 
are only small primitive-tubes); these tubes consist of a neuroglia- 
sheath, and a semi-fluid contents (hyaloplasm), they have conse- 
quently a structure similar to the primitive-tubes of the nerve-tubes,. 
only that their sheaths are stronger than the spongioplasmic ones- 
of the latter. 
The tubes and fibrillæ forming the dotted substance do nof 
anastomose with each other, but form, only, a more or less intricate 
web or plaiting. The reticulation seen in sections, and described by 
various authors as a real nervous reticulation, is no reticulation, 
but is produced by the transsection of the tubes forming the dotted 
substance, and the meshes of the reticulation are only the transsected 
sheaths of these tubes. The „interfibrillar substance", described by 
various authors, is the hyaline hyaloplasm, which forms the contents^ 
of the tubes, and is the real nervous substance.^) 
1) I think it probable that it is the same substance which Bawitz describes- 
as myeloid substance. Hermann'?, »Zwischensubstanz« (cf. p. 46) is evidently 
hyaloplasm. The »Knotenpunkte«, described by Hermann, are, I suppose, thicke- 
nings in the sheaths of the tubes, they can not be neuroglia-nuclei, as they seem 
to occur in too great abundance. 
