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sessing great resemblance to that of the lateral line. The outer layer 
of the optic cup, i. e. that which gives rise to the pigmented coat, 
developes no fibres, and this seems also to be the case for its con- 
tinuation into the optic stalk; for when the cup joins the stalk the 
outer (“choroid”) layer passes into and forms the dorsal portion of 
this structure, and here, as indeed is clearly to be seen in FRORIEP’S 
diagrams, no fibres are laid down. 
The fibres of the nerve begin to be formed from the true basal 
portion of the retinal neuroepithelium, that is, on the side next to the 
vitreous humour. As FRORIEP convincingly demontrated, the direction 
of growth isthence to the base of the cup, and then onwards towards 
the brain along the ventral surface of the optic stalk. The reason 
which has induced a reference to the development of the optic nerve 
is that, as already stated, the mode in which its fibres are formed 
resembles that origin in situ from the cells (nuclei or nerve-chains) 
of a neuroepithelium previously described in the case of the lateral 
nerve. In the optic nerve, too, it is the basal side of the epithelium 
which gives rise to the nerve, while, as is well known, the perceptive 
elements are developed in connection with its outer side. The points 
here raised are difficult of explanation without the aid of figures, but 
the phenomena are interesting as justifying the statement that the 
development of the lateral nerve would apparently serve as a paradigm 
for many other processes in the ontogeny of the central nervous system. 
The view I am led to adopt harmonises in some respects with that 
taken by LIEBERKÜHN and BALFOUR. FRORIEP’S conclusion appears 
to be a similar one, for he speaks of the oldest fibres as arising 
“von Zellen in der Nähe des Augenblasenstieles”, but it must be con- 
fessed that beyond the recognition of the true direction of growth, 
his standpoint is not well defined. 
The ontogeny, therefore, demonstrates why the fibres of the optic 
nerve pass to the base of the brain, — because they are developed 
from the epithelial cells of that region. 
‘ In an extended account of these researches a detailed notice would 
be bestowed upon VıGnAL’s work on nerve histogenesis 1). The actual 
observations of this investigator seem deserving of the highest praise, 
and it is only, or rather mainly, in his interpretations of the bearings 
of observed facts that Vıcnan’s conclusions would be challenged. 
1) Vıenar, W., Développement des éléments du systéme nerveux céré- 
bro-spinal, Paris 1889. — Köruıker’s important observations would also 
come under review; i. e. as to the validity of his interpretations. 
