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the fibriUar plaiting — or they maintain their individuality, and pass 
through the dotted substance and into a peripheral nerve, forming a 
nerve-tube. They have, however, no isolated course, and give off 
extremely slender fibriUar branches to the fibrillar plaiting, on their 
way through the dotted substance. The nerve-tuhes have hvo modes 
of origin, they — either spring directly from ganglion cells (witliout 
isolated course as above mentioned) — or indirectly, from the 
fibrillar plaited texture. 
Franz VON Wagner (1886) who, at the same time as I myself, 
has described the nervous system of 3Iysostoma^) supposes the 
nerve- fibr es or nerves-) to have only an indirect origin; i. e. in the 
»Punktsubstanz«, which he believes to be »ein dichtes Geflecht 
feinster Faserchen, welche aus der pinselformigen Auflosung der 
protoplasmatischen Fortsatze der GangUenzellen hervorgehen. Aus 
diesem maschigen Filz treten die Nerven heraus.« »Das schwammig- 
netzige Gefuge«, which Leydig describes, in »Zelle und Gewebe«, 
v. Wagner has also observed; his opinion of the nature of this 
substance he does not, however, give. 
Towards the close of last year another paper by BÉLA Haller 
appeared. In it the author states his results of some investigations 
on the structure of the nervous system of Annelids, Arthropods 
(Tobanus bovinus) and some Vertebrates. He compares these 
results with his previous description of the nervous system of the 
Mhipidoglossa. In the dotted substance of the latter he found 
no connective tissue, the substance consisted, exclusivcly, of a central 
nervous reticulation springing from the processes of the ganglion cells. 
In those firstmentioned animals the case is different. In their nervous 
system the dotted substance is formed by a reticulation of connec- 
tive-tissue, as well as by a real nervous one. 
This is a description very similar indeed to that which Bellonci 
already, some years ago, on several occasions. has given of the central 
nervous system of Crustaceans as well as Vertebrates. Haller 
seems however not to know this Italian author. 
In his opinion the nervous system of the Mollusca represents, 
thus, a very primitive state, being difficient in a reticulation of con- 
nective tissue, it is in this respect like that of Coelenterates. In inverte- 
^) I have previously menlioned the memoir of Wagner in a paper on the 
nervous system of Myzostoma, which will, I hope, soon appear in «Jenaische 
Zeitschr. fiir Nat.« 1887. 
2) v. Wagner does not believe that the nerves of the Myzostomes are really 
differentiated into fibres (vide 1. c. p. 48.) 
