— 122 — 
4) The contents of the nervous processes consists of primitive 
tubes which spring from the protoplasm of the ganglion cells, 
generally in such manner that they converge uniformly from the 
whole protoplasm, towards the pole where the nervous process 
issues; here they unite, and constitute the contents of the latter 
(fig.s 26, 43—58). 
In some ganglion cells (observed in Homarus and Nephrops) 
the contents arises from a union of bundles of primitive tubes. The 
contents of the nervous process may also be formed, in this or the 
common manner, within the protoplasm of the cell for a shorter or 
longer distance from the place where the process issues, the process- 
contents has thus, to some extent, an undivided course through the 
protoplasm within the cell itself (fig.s 37, 38 A, 59, 60). These latter 
modes of origin I have observed especially in Homarus and Nephrops. 
3. The structure of Leydig's dotted substance. 
The nature of the so-called Leydigs dotted substance (»Punkt- 
substanz«), which is centrally situated in the nervous ganglia or the 
central nerve-system of all invertebrated bilaterates, has been very 
much discussed, and has been described in very different ways by 
the many previous authors on this subject, as is already mentioned 
in the historical introduction to this paper. 
Where so many prominent scientists have given their opinion, 
it is, of course, a serious matter to suggest a new view which is 
contrary to almost all previous views. ^) It was therefore not with- 
out some hesitation and only after careful investigations that I 
entered upon the description of the dotted substance in the nerve- 
system of the 3Iyzostomes-) and subsequently upon the dotted sub- 
stance in the brain of the Ascidians.^) Since that time I have 
extended m}.^ investigations to a great many animals of various 
classes, and have always found my previous results confirmed in 
the principal respects. 
My investigations lead me, thus, to maintain the view I have 
previousiy stated, and I am now in a position to state it, as I 
^) Leydig is, as before mentioned, the author with whom I can agree in 
most respects. 
2) 1. c. 1886. 
•■') 1. c. 1886. 
