155 
I have verified this upward growth in Raja, it can be made out 
both in surface views, and also in sagittal sections. At an early stage 
a portion of the roof can be distinguished from the rest, as a layer 
of cells not possessing the characters of neuro-epithelium, this gives 
rise to the epithelial basis of the choroid plexus !) of the third ventricle, 
a structure which is represented in the highest Vertebrates, and even 
in man. When we consider that the epithelial coat of this choroid 
plexus is in reality the homologue of the whole epithelial lamella or 
pallium of the Teleostean or Ganoid, and that it has, in spite of the 
enormous increase of grey matter, undergone no change, even in man, 
one wonders when and where the future, so confidently foretold for 
it by RagL-RückHARrp, is to begin! 
The so-called pallium of Teleostei, Ganoidei, and Marsi- 
pobranchii has everything in common with the plexus choroideus 
of higher forms: while it has nothing to do with the structure to 
which the same name is applied in Selachii, Dipnoi, Amphibia, 
Reptilia, Aves and Mammalia. 
The latter nervous structure is derived from such an organ as 
the so-called corpora striata of Ganoidei, Teleostei and Marsi- 
pobranchii. I do not say that it is derived from that piece of 
tissue, as it exists in any of these forms; because at present nothing 
very definite can be stated of the ancestral forms of the Selachians etc. 
— The probability appears to be that the Dipnoi and Selachii, 
and the ancestors of higher forms, arose from a group of fishes allied 
to the Proto-Ganoidei — of that more anon. I do, however, 
strongly insist that what we call the corpora striata in Ganoidei, 
Teleostei and Marsipobranchii contain within them the po- 
tentialities of the greater developed fore-brain in other forms, if these 
potentialities are present in any part of the Teleostean or Ganoid brain. 
The pallium of these sub-classes contains no power of forming either 
nerve cells or nerve fibres. 
So far as I am aware, the only author who has dissented from 
the current view is Dr. W. H. GAsKELE, who in a recent publication ?), 
along with views which no morphologist can regard with the slightest 
favour, states (p. 195): „I can see no evidence to show that the thin 
1) Perhaps it may not be out of place to remark that the choroid 
plexus always is made up of blood vessels and a layer of epithelium 
roofing in the region of the brain over which the plexus lies. 
2) Gasxett, W. H., On the relation between structure, function etc, 
together with a theory of the origin of the nervous system of Verte- 
brates. Jour. of Physiol. Vol. X, Nr. 3, p. 153 ete. 
