578 Proceedings of the Royal Society 
Furtherj the perfect development of the true maxillaries, indi- 
cated by the invariable presence of the canines, is significant of the 
lesion being one chiefly affecting or originating in the interposed 
structures ; and in the more characteristic cases the disease no 
doubt is best marked in its effects on the intermaxillary bones. 
Without homologating any hypothesis advanced on such subjects, 
this proclivity to irregular or arrested development in these bones 
— the hasmal spines of the nasal vertebra, as described by Owen — 
the hsemapophyses of the catacentric vomerine sclerotome, as 
described by Gfoodsir, — seems to afl’ord a confirmation of the theory, 
that the tendency to return to a manifestation of what have been 
described as archetypal characters ; or, on the other hand, to 
assume an erratic development, becomes greater as we depart from 
the vertebral centrum. This part of the subject is one, however, 
which, without mature elaboration of many as yet undetermined 
facts bearing on it, cannot be treated in either a positive or an 
exhaustive manner. But in a further acquaintance with those 
great principles of morphology, of late beginning to be revealed in 
the vertebrate skeleton, we may expect that the nature of malfor- 
mation and metrological disease will be presented in a new and 
more intelligible light. 
5. Notes more especially on the Bridging Convolutions in 
the Brain of the Chimpanzee. By Wm. Turner, M.B., 
F.R.S.E. 
The late Professor G-ratiolet, in his elaborate and beautifully 
illustrated memoir, “ Sur les Plis Gerebraux de THomme et des 
Primates,” attaches great weight in his differential diagnosis of 
their cerebral characters to the presence or absence of one or more 
members of a series of convolutions, which he designates as the 
ylis de passage. When present, these convolutions bridge over the 
external perpendicular fissure of the hemisphere, and connect 
the parietal and temporal with the occipital lobes. By various 
anatomists in this country they are called bridging, connecting, 
or annectent convolutions. In the brain of the Chimpanzee M. 
G-ratiolet states that the first bridging convolution is altogether 
