1898] NOTES AND COMMENTS 371 
face, also more slender limbs. Continual in-breeding tends to keep 
the jaws and face elongated and the limbs slender; while the 
frequent accession of new blood has precisely the reverse effect. In 
connection with this Prof. Branco ingeniously remarks, that in early 
Tertiary times, when there were much fewer mammals than in later 
times, in-breeding must have been comparatively common and may 
thus account for the universal long jaws and numerous teeth 
characteristic of all genera of the period. 
A second cause of the reduction of the mammalian dentition is 
the preponderating growth of one or more of its components ; such 
as the excessive development of the canines in Sus, and of the last 
molar in Phacochoerus. 
As already long recognised, teeth also disappear when their 
function is lost. Hence the loss of the upper incisors in ruminants 
and most of the incisors in elephants, when the tongue and the trunk 
respectively usurp their functions. Hence also the loss of canines 
when effective weapons in the form of horns appear. 
Finally, it follows from these considerations that changes in the 
mode of life and feeding have always been most potent factors, not 
only in modifying the individual teeth, but also in tending towards 
their reduction in number and the preponderating development of a 
few. 
A New PERIPATUS 
A Goop deal was said about the Peripatidae in the pages of Natural 
Science in connection with the publication of the fifth volume of the 
Cambridge Natural History, and in the series of short articles giving 
the opinions of various experts on the classification and constitution 
of the Arthropoda. Since that time the literature of this interest- 
ing family has been enriched by several papers, by far the most 
important of which is Dr Willey’s memoir on the species he procured 
in New Britain (see Natwral Science, vol. xiii. p. 280). New Britain 
is an island lying off the east coast of Papua and forming part of 
the Austro-Malaysian sub-region of the Australian Region of Sclater 
and Wallace. Hitherto no member of this group had been dis- 
covered in this area, although several species have long been known 
from the adjacent sub-regions of Australia and New Zealand. One 
species too has been recorded from Sumatra; but some authorities, 
including Dr Willey, seriously doubt the accuracy of this locality 
on the grounds that this alleged Sumatran species is apparently 
generically identical with the Neotropical members of the family. 
Other zoologists, on the contrary, not unmindful of such facts as 
the distribution of the existing species of tapirs in the large Malay 
islands and in tropical America, are not quite so sceptical and see 
1 Vol. viii. pp. 122, 215, and 285; vol. x. pp. 97 and 264. 
