THE FISSURA HIPPOCAMPI 95 
is no interruption of the fissure. Ventral to this fissure is that 
of the choroid plexus, whose taeniae he so near each other that 
there is no apparent opening. 
The caudal pole of the growing hemisphere attached above 
the telencephalic limit of the di-telencephalic groove is swinging 
antero-ventrally and carrying with it new tissue, that of the de- 
veloping neopallium. Consequently the vault is not only increas- 
ing in height above the ventral ventricular eminences, but is also 
increasing in extent simultaneously with the forward and down- 
ward growth of the temporal pole. 
The 32.1-mm. embryo, University of Chicago, H 41 (figs. 22 and 24, 
pp. 116 and 117, Barley, ’16 a) 
The most striking aspect of the ventricular surface of the 
thalamus is the deepening of the rostral end of the sulcus limitans 
and the progressive fading of the sulcus dorsalis. The region 
which lies between these two grooves occupies the major portion 
of the ventricular thalamic surface. Dorsal to the sulcus dorsalis 
lies a ridge in the midline which is accentuated in the model by 
the irregular trimming of the diencephalic roof plate. This ridge 
was described by His as containing the stria medullaris and the 
habenula. It is interesting to note that its anterior end reaches 
the lateral limb of the velum transversum, while its ventral 
border (the sulcus dorsalis) ‘gradually fades out anteriorly in 
the same region. Consequently, the foramen interventriculare 
is closed posteriorly by the great midthalamus. The hypothala- 
mus remains almost unchanged. Optic fibers are present in the 
chiasma ridge. The recesses which lie anterior and posterior 
to the chiasma ridge are deepened. The infundibulum opens 
into the cavity of the posterior lobe of the hypophysis. The 
tuber cinereum is thin. The mammillary recess is very shallow. 
The rostral end of the sulcus limitans joins the suleus which 
separates the hypothalamus from the medial limb of the corpus 
striatum, and runs over the floor of the foramen interventriculare 
into the basal portion of the lateral ventricular surface of the 
diencephalon. This portion of the corpus striatum together 
with the dorsal part of the lamina terminalis forms the anterior 
