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lich ordnen sich die Fibrillen neuerdings zu verschieden starken 
Biindeln aus denen die peripheren Nervenstamme sich entwickeln« 
(1. c. 1877 p. 24). He does not, however, deny the possibility of a 
direct origin of nerve- tubes existing. »Ich habe aber unter gewohn- 
lichen Verhaltnissen nur ein solches Verhalten nicht mit untriiglicher 
Klarheit zur Anschauung bringen konnen« (1. c. 1878 p. 487). 
Rabl-Ruckhard (1875), in his paper on the brain of the ant, 
has scarcely paid much attention to the histology of the brain. He 
calls the dotted substance »jener feinkornigen, homogenen, keine 
Zellenstructur zeigenden Substanz, die so vielfach an der Bildung des 
Centrahiervensystems der Arthropoden betheiligt ist« (1. c. p. 489), 
and his mention of this subject almost confines itself to that. 
Plogers paper on the brain of Insects (1878) has scarcely any 
more interest for our present researches as neither has he paid any 
particular attention to the nervous elements. In the fibrillar parts ol 
the brain, he distinguishes between masses of »netzf6rmig gestrickten 
Substanz« and masses of »långsfaserigen Substanz«, of which he gives 
no distinct description. The real structure he has not recognised; 
he says for instance (1. c. p. 561) that the fibres of this »långsfase- 
rigen Substanz «, transversally transsected, have the appearance of 
points or dots (»bei Horizontalschitten erscheint das Ganze aus zahl- 
losen Punkten zusammengesetzt«). As far as I have seen he does 
not mention the relation of the nerve-tubes to the ganglion cells; 
judging from his various descriptions I think, however, that he 
supposes an indirect origin (i. e. in the central fibrillar substance) of 
the tubes or fibres, as he would call them, to be the rule. 
E. Berger (1878) maintains a direct origin of the nerve-tubes 
from ganglion cells; this he has been able to, especially, observe 
in connection with the origin of the antennal nerve-tubes in Musea 
vomitoria which he therefore recommends as a good subject for 
examination to convince oneself of this mode of origin. He does 
not, however, deny that an indirect origin may possibly occur, and 
believes it, even, to be probable (1. c. p. 3). 
YUNG (1878) believes in a direct origin of the nerve-tubes 
from ganglion cells. »Les tubes, « he says, »ne sont bien en 
réalité que de simples prolongements cellulaires.« Still it seems as 
if he, to a certain extent, e. g. in the origin of the nervi optici, 
supposes a kind of double origin (direct and indirect.?) to exist, 
this origin is not, however, definitely explained (p. 454). His 
view of the central fibrous substance seems to be of a some- 
