No. 1.] AMPHIBIAN BRAIN STUDIES. 83 
The optic lobes form single, unpaired bodies, as in many of the 
Urodela. The infundibular lobes in both orders are large and 
functional. The cerebellum is small! and partly overhung by 
the mesencephalon. 
In a few respects the brain of Protopterus differs: the gan- 
glia habenarum are much larger than in the Urodela, resembling 
those of Petromyzon. The anterior portion of the metencephalon 
is greatly expanded by the hypertrophied nuclei of the 5th—8th 
nerves and a diverticulum of the 4th ventricle. The olfactory 
nerves arise from the dorsal aspect of the rhinencephalon. 
The similarity in the internal structure is very significant. 
The general arrangement of the encephalic gray substance, as 
the central gray, immediately surrounding the ventricles, is the 
same ; the dipnoan efendyma has the peculiarity, first observed 
by Stieda in Rama, of the thread-like extensions of its cells 
through the central gray into the white substance; we also ob- 
serve the peculiarly modified elongate ependymal cells (Fulli- 
quet, Pl. IV. Fig. 17, cde), in the region of the posterior com- 
missure, so characteristic of the Uvodele brain. As these ob- 
servations were prior to the discovery of the true nature of the 
pineal gland, the author has naturally failed to identify this 
structure, mistaking the ganglia habenarum for it (Fig. 19). 
The relation of the dia- and procceliz seem to resemble those 
of Rava more closely than those of the Urodeles, since, as far 
as I can judge from Figs. 19 and 20, the prosencephalic com- 
missures are in the /amina terminalis proper, and not in a pro- 
jection of the floor of the ventriculus communis, as in the 
Urodela. The space marked TM in Fig. 19 represents this 
ventricle. 
The encephalic commissures of Protopterus? apparently agree 
advantage of the anterior and posterior boundaries of the Diencephalon (Entrencé- 
phale), as defined by the posterior and superior commissures. 
1 As there is no sagittal section of the Protopterus brain given, it is somewhat 
difficult to determine the limits of the cerebellum. A portion of the brain desig- 
nated Cervelet (Plate I.) is apparently a portion of the hypertrophied nucleus of the 
trigeminal nerve. 
2 Fulliquet has not distinguished the posterior or superior commissures as such; 
nor has he identified the upper bundle in the lamina terminalis with the corpus 
callosum, as seems highly probable. It follows that my determination of these com- 
missures is largely inferential from a comparison with similar sections of the Urodele 
brain. 
