297 
cases at least they may have wandered to the recently formed fibril 
from some other place. This point has received some notice in con- 
nection with the nerves of the transient ganglion cells !). 
The mode of formation of the neurilemma is perhaps of compa- 
ratively little importance); but, for a long time, I had thought it 
possible that this structure might not be a product of the nerve- 
forming cells. Its well-known absence in certain cases formed my 
chief stumbling block. Now, but not without reserve, I am inclined 
to regard it as a product of the nerve-forming cells, possibly as a 
modification of the cell-protoplasm. 
The development of the chain of cells, which goes to form the 
nerve connecting any sense organ with the main trunk of the nerve, 
had also been observed and figured for publication. In this respect 
I have seen what Dourn figures on plates 17 and 18 of his memoir. 
A further account may by reserved. 
b) The histogenesis of motor nerves, cranial and spinal. 
The histogenesis of motor spinal nerves repeats the history of 
such a nerve as the lateralis, if the region, which will become the 
anterior horn of the spinal cord, be looked upon as the parent neuro- 
epithelium. The chains of cells leave the cord in a manner often 
described, and finally detailed by Dorn in more than one publication. 
The blunted peripheral termination of the chain becomes applied to 
the muscle-plate, and, with great certainty I can repeat what I have 
already more than once stated, that the terminal end-plates of muscle 
and of the electric organ are formed from the wandering of such cells 
1) A nerve chain of a very simple nature, consisting of a single 
linear row of cells, is very frequently met with in the development of 
(a) small nerve twigs, and (b) axis-cylinders of the transient nervous 
apparatus. Such examples are of a very striking character, and only 
with difficulty was the temptation to figure them here resisted. I have 
already figures of many such cases where the component cells remind 
one of a squad of soldiers in single file. Afterwards by the “spinning” 
of an axis-cylinder they become in a sense connected. 
2) Except in relation to the nature of the neuroglia. (Vide Donen, 
Studie 17, p. 328). This is a matter, which had hardly entered into the 
scope of my observations; although I had seen sufficient to cause me to 
reject for Selachians the views of His as to the “Gerüst” (see His’ 
Archiv, Suppl.-Band 1890, pp. 96—98). To Donern’s remarks (p. 328) 
it may be permissible to add that G. Fritsch (Arch. f. mikroskop. Anat., 
Bd. 27, p. 14 and Monatsberichte der Kgl. Akad. Berlin, 19. Juli 1875) 
has already urged that ganglion cells, ”glia‘“ cells etc. would appear to be 
”verwandte Bildungen“. In this question my studies lead me to side with 
Fritsch and Donen. 
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