MORPHOLOGICAL STUDIES. 
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Marshall’s position is not quite so simple. The cranial 
nerves (and ganglia) of the Chick Marshall (No. 46) refers to 
the re-entering angle between the neural plate and external 
epiblast, but nothing definite is stated as to the relations of this 
portion of the epiblast to the external epiblast on the one hand 
or to the brain on the other. In other words, if we are entitled 
to conclude that Professor Marshall held the independent epi- 
blastic origin of cranial nerves and ganglia, we miss in the 
account the necessary denial of Balfour’s view as stated above. 
If Marshall recognised the epiblastic origin of the neural ridge 
he did not tell us whether or not he holds with Balfour that it 
“ clearly belongs to the brain.” This is important, for taken 
in connection with his acceptance of Balfour’s view of the origin 
of spinal ganglia, it does not preclude the possibility of the 
assumption that the neural ridge in the Chick arose from a por- 
tion of the brain which has not got shut in. Professor Marshall 
has indeed seen and described part of the true origin of the 
cells which form the neural ridge in the Chick. The whole 
of the source he has not identified, and he did to draw the 
conclusions of the independent origin of the ganglia to which 
he was entitled. 
The part he had not seen is that portion of the cranial 
ganglion Anlage which is formed from the external epiblast 
outside the angle between epiblast and brain. This was first 
seen by Onodi (No. 51). 
Judging from the following passage, it would appear as 
though Professor Marshall held the origin of the ganglia to be 
the same in both brain and cord, and the difference to be only 
as to the time of closure of the neural canal. He says (No. 46, 
p. 16): “Its (the neural ridge) first appearance precedes the 
closure of the neural canal, but after about the fortieth hour the 
closure of the canal proceeds backwards more rapidly than the 
growth of the neural ridge, so that in the greater part of the 
length of the spinal cord the ridge is developed as an out- 
growth from the summit of the cord itself, and never 
has any connection with the external epiblast.” 
In order to get a little nearer Marshall’s position 1 turned to 
