242 University of California Publications in Zoology [Vov.17 
The second authority, Andersen (1912, p. Ixxvi), observes: 
The evidence afforded by the geographical distribution of Bats has generally 
been considered of doubtful value; hence they have either been entirely excluded 
from the material worked out by zoogeographers or at least treated with pro- 
nounced suspicion, as likely to be more or less unreliable documents of evidence. 
This unwillingness or hesitation to place Bats on an equal zoogeographical footing 
with non-flying Mammalia would seem to be due, partly to the preconceived idea 
that owing to their power of flight Bats must evidently have been able easily to 
spread across barriers which, in ordinary circumstances, are insuperable for 
wingless Mammalia; partly to the fact that hitherto very often whole series of 
distinct forms have been concealed under one technical name. So long as (to 
mention only three cases among many) ‘‘ Macroglossus minimus’’ was believed to 
range unchanged from the Himalayas to New Guinea, Australia, and the Solomon 
Islands (now two distinct genera, thirteen recognizable forms), or ‘‘Cynopterus 
marginatus’’ over India, Ceylon, Indo-China, and Indo-Malaya (now six species, 
fourteen forms), or ‘‘ Rhinolophus ferrum-equinum’’ uniformly over Europe, Asia, 
and Africa (now numerous distinet forms), they were undoubtedly of questionable 
value as zoogeographical material. But these and similar anomalies invariably 
disappear as soon as modern methods of discrimination applied on vastly in- 
creased material render it possible to draw the lines of separation between the 
species (and their local modifications) somewhat more closely in accordance with 
the lines drawn by Nature. The second argument referred to above, that the 
spreading of Bats from one locality to another must obviously have been greatly 
facilitated by their possession of wings, may in theory appear plausible enough, 
but when tested on the actual distribution of the species and subspecies it proves 
to be of much less importance than commonly supposed; it rests, in reality, on 
a confusion of two different things: the power of flight no doubt would enable 
a Bat to spread over a much larger area than non-flying Mammalia, but, as a 
matter of fact, only in very few cases is there any reason to believe that it has 
caused it to do so. 
Matthew (1915, p. 227) remarks with regard to this paragraph: 
The belief that bats are more easily able to cross ocean barriers than non- 
flying mammals is probably based, not on the preconceived idea that they could, 
but upon the plain fact that they have done so far more frequently. Birds and 
bats are found upon numerous oceanic islands where no non-flying mammals, 
and very few non-flying animals at all, exist. That they have wings and occa- 
sionally use them for so long a journey, whether voluntarily or involuntarily, is 
a natural explanation. I cannot see any other reasonable interpretation of the 
fact that they are present and the terrestrial mammals absent in so many remote 
oceanic islands. With bats, as with most birds, the intervening ocean acts as a 
hindrance, but their wider distribution shows that it is less of a hindrance than 
with terrestrial mammals. 
Matthew’s comments are good, so far as they go, but it seems to 
the present writer that he has missed the main point of the thesis, 
which is, that conditions of temperature and humidity limit the dis- 
tribution of bats as strictly as they do that of other groups of mam- 
mals. Of course, given a chain of islands of identical climatic con- 
ditions, the distribution of bats would without doubt be more uniform 
