206 G. ELLIOT SMITH. 
Fie. 9.—(No. 38). Passing just in front of the foramen of Monro on the 
right side, and through it on the left. References as above. 
Fie. 10.—(No. 47.) Through foramen of Monro (f 4). a.ec. Anterior 
commissure. ¢h. Optic thalamus. Bf The “hippocampal furrow” 
(Bogenfurche). 
Fie. 11.—(No. 51.) Just behindthe foramenof Monro. /.f. Longitudinal 
furrow. 7.0. Recessus opticus. pdf. Pituitary gland. G.g. Gasserian gan- 
glion. c.¢. Internal capsule. 
Fie. 12.—(No. 80.) y.4. Ganglion habenule. z.¢4. Nucleus thalami 
(centre mediane de Luys). 7.s¢. ‘ Radiatio strio-thalamica” of Edinger. 
¢.s. Stria terminalis (running horizontally). G@.g. Gasserian ganglion. Viz, 
Fibres of fifth nerve proceeding from G.g. to the pons. 
Fic. 13.—(No. 89.) z..a. Nucleus amygdala, from which the large stria 
terminalis (¢.s.) arises and passes vertically upwards to cross on the dorsal 
aspect of the radiatio strio-thalamica (7. s¢.). pos. The “ tuberculum quinti” 
of the pons Varolii. 
Fic. 14.—Section through the adult Ornithorhynechus brain corre- 
sponding to Fig, 12 in the foetus. x 2. References as above. m.c. Middle 
(soft) commissure. p. swb¢. Pars subthalamica (hypothalamus of Waldeyer). 
Vie. 15.—Part of Fig. 9 enlarged. B/ Hippocampal furrow (Bogenfurche). 
ch. 3. Median choroidal invagination (diaplexus). Ap. Hippocampus. /. d. 
Fascia dentata. p. Pallium. c.s. Corpus striatum. d./. Descending fornix 
fibres. 2. xf. Lamina infra-neuroporica. 
Fic. 16.—Coronal section through the corresponding region of an early 
foetus of Perameles nasuta. c#./. Choroid plexus of the lateral ventricle. 
Fig. 17.—Section a short distance behind Fig. 16. ¢4. Optic thalamus. 
J. M. Situation of foramen of Monro. Bf Situation of Bogeufurche. 
Fic. 18.—Z.s. Olfactory bulb of foetal Platypus. x 25. olf.g. Olfactory 
ganglion. J.g. Olfactory ganglion into which the nerves from Jacobson’s 
organ are inserted. j. Nerve-fibre layer. d. Layer of nerve-cells. ¢. Hpen- 
dymal layer surrounding the ventricle. 
Vie. 19.—Neuroblasts (Zeiss D) from d, (Fig. 18). 
Vic. 20.—Supra-ventricular cortex cerebri (pallium) of feetal Platypus. 
x 96. a. Kpendymal layer. e. Deep nerve-cell layer (Rolando-cell layer of 
Lowe). d. Middle fibre layer. ¢. Superficial nerve-cell layer (mantle layer). 
J. Superficial fibre layer (molecular layer). 
Fies. 6, 7, 9, 10, 11, 12, 18, 16, 17, and 18 were drawn by means of a 
camera lucida. Fig. 15 was drawn from a microphotograph, for which I am 
indebted to Professor Wilson. 
