270 EDWARD PHELPS ALLIS, JR. 
and he definitely decides in favor of the latter supposition. 
Fuchs, however, decides just as definitely in favor of the first- 
mentioned supposition, for he says (12, p. 104) that, in Che- 
lone, the trabeculae take no part in the formation of the septum; 
that the septum is a new formation, peculiar to the tropibasic 
cranium; that it first appears as a keel-shaped outgrowth (Vor- 
wolbung) on the ventral surface of the primordial basis cranii, 
and that it increases in height by growing upward. How a 
ridge on the ventral surface of the basis cranii could increase 
in height by growing upward is not at first quite clear, but in 
certain of the figures given by Fuchs the fundament of the 
septum is shown lying between the trabeculae, and hence ca- 
pable of growing upward between them. This would of course 
leave the trabeculae near the ventral end of the septum, and 
this is the position in which they are shown in one of the figures 
given by Fuchs (I. c., fig. 16 b). It is further said that, in later 
stages of development than that shown in the above-mentioned 
figure, the trabeculae are no longer recognizable in the optic 
region, but persist in the region of the hypophysis and from 
there run forward and fuse with the lower, thickened portion 
of the septum interorbitale. It is, however, particularly said 
by Fuchs that the ventral portions of the side walls of the cra- 
nium are here formed by the trabeculae, and that, in the em- 
bryo shown in his figures 16a and 16b, the trabeculae, in the 
region anterior to the nervus opticus, are reduced to connective 
tissue cords which lie near the upper end of the septum. 
There is thus a difference of opinion as to the manner in 
which this septum arises, and there would also seem to be some 
confusion in Fuchs’s statements regarding it. My own work 
leads me to suggest that the epichordal and hypochordal bands 
of skeletogenous material, known to be developed in the spinal 
region of embryos, are continued forward into the prespinal 
region, and that the trabeculae are there developed from them. 
These two morphologically distinct portions of the trabeculae 
are fused to form the basis cranii in the orbital region of the 
platybasic cranium, just as they are always fused, in embryos, 
to form the parachordal plate in the prootic region, and usually 
