is remembered that my somatic area lies for the most part in the 
region known to KAPPERS and others as the praethalamus. It is only 
since the publication of the writer’s paper on the Morphology of the 
Forebrain Vesicle (1909) that this region has been recognized as a 
part of the telencephalon at all. On what ground, then, does KAPPERS 
state that this area receives chiefly secondary olfactory fibers? 
The grounds for recognizing a corpus callosum in selachians are 
stated in both the papers to which Kappers refers (1910c, 1911a). 
c.p.a.? 
Fig. 6B. 
Fig. 6. A, diagram of the fornix and the tractus pallii in Seyllium. B, diagram 
of the tractus pallii in Chimaera. Only the uncrossed portion of the tractus pallii is 
shown in both diagrams. At X is the vertical bundle to which KAPPERS has given 
the name tractus medianus in Chimaera and Galeus. The diagrams show that the name 
is applied to two entirely different tracts in the two forms. c.p.a. commissura pallii 
anterior. r.n. recessus neuroporicus. The arrow in A shows the direction of the 
rotation necessary to produce the forebrain of Chimaera from a typical selachian brain. 
The bundle in question is a true commissure lying in the lamina supra- 
neuroporica and connects areas into which enter tracts from the ge- 
neral sensory and optic centers in the thalamus. These areas do not 
receive secondary olfactory fibers. ‘These areas send down tracts which 
are separate from all the olfacto- hypothalamic tracts and end in the 
