125 
further back that the disproportionate increase in the breadth of 
the Stratum granulosum (as compared with the layer of polymorphous 
cells) causes it to bulge (together of course with the Str. moleculare) 
towards the fissura hippocampi (Figs. 3 and 4) as a finger-like process, 
which carries with it a core from the layer of polymorphous cells (Fig. 5). 
If Fig. 2 to 5 be compared with one another it will be evident that 
Fig. 3. Fig. 5. 
Oo 4, ve ID 
tr 9 ~ 
ie ur / 
Rs 
NV 
S x‘ 
S N 
S % > 
= ~~. 
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U 
SITES of 
> = 
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A N 
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Er 
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1 
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Fig. 5. Scheme of hippocampal formation of Örnithorhynchus immediately in 
front of the region of the commissures. 
whereas the Stratum granulosum has increased enormously in breadth, 
the layer of polymorphous cells has remained practically unchanged, as 
its relation to the precommissural area and ventricle clearly indicates 
in the series of schemata. It is also clear that the folding of the 
Fascia dentata (a) does not involve the whole thickness of the brain 
wall, but only its superficial part and (b) that this folding is the direct 
result of the disproportion between the rates of growth of the super- 
ficial and the deeper regions of the cerebral wall. 
There would appear, therefore, to be some justification for re- 
stricting the term “Fascia dentata” to the Stratum granulosum and 
