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the basal olfactory centers. I made no mention of the “dorsal part 
of the striatum” in the whole paper. 
Third, KApPpErs refers on p. 10 to my short paper on Chimaera, 
“worin JOHNSTON den von THEUNISSEN und mir gemachten Befund be- 
stätigt, daß der Tr. medianus des Vorderhirnes, bis jetzt als ein dem 
Vorderhirn eigenes Bündel betrachtet, kaudalwärts verläuft und in dem 
Thalamus endet”. This sentence contains three misstatements. a) I did 
not confirm the description of this tract by KAPPERS and THEUNISSEN, 
but severely criticized it. b) The tract in question does not end in 
the thalamus but chiefly arises in the hypothalamus, from which 
it ascends to the forebrain. c) The tr. medianus had been described 
by Kapprrs (1906, pls. X and XIII) not as a tract confined to the 
forebrain but as going in the basal bundle to the diencephalon. What. 
I did was to show that KAPPERS and THEUNISSEN had wrongly iden- 
tified what they called the tractus taeniae in Chimaera with what Kap- 
PERS had called the tractus medianus in selachians. The tractus me- 
dianus in selachians is the fornix column which arises in the roof, 
bends down around the rostral wall and runs caudad in the basal 
bundle. The “tractus taeniae” of KAPPERS and THEUNISSEN in Chi- 
maera is homologous with a part of the tractus pallii in all fishes, 
which arises in the hypothalamus and runs forward to the roof in 
selachians. In Chimaera, owing to the stretching forward and rotating 
downward of the massive roof, the tract follows the roof down in the 
rostral wall. This rostral wall, however, is morphologically the same 
as the roof in selachians. I give here two diagrams (Fig. 6) to illus- 
trate the course of the ‘tractus medianus” or fornix in selachians 
and the tractus pallii in Chimaera in the hope that further confusion 
in this matter may be avoided. 
KAPPERS severely denounces the writer’s hypothesis that a corpus 
callosum is present in selachians. Let it be understood at once that 
this idea holds still in the writer’s mind the place of an hypothesis; 
an hypothesis, however, which grows more and more probable as my 
work proceeds. KAPPERS refuses to consider the evidence on which I 
based this hypothesis, saying only “Gute Gründe ..... sind nicht zu 
finden” (p. 13). He asserts that the area from which my corpus 
callosum arises receives chiefly secondary olfactory fibers. When I 
was studying the selachian brain I was unable to find that KAPPERS 
(or any other author whose work was accessible to me) had ever made 
any mention of the region described by me under the name of somatic 
area. The view that this area receives secondary olfactory fibers is 
a pure assumption. This assumption is the more surprising when it 
