142 . ORIGIN, ETC, OF THE FAUNA. 
Appendix. 
The recently published paper by W. D. Matthew, entitled “Climate and Evolution” 
(Ann. New York Acad. Sci. xxiv. pp. 171-318, Feb. 1915), came to hand after the 
Mamunalian section of this work was in type and after the sections dealing with 
the Arthropoda were written. Two of the main propositions of this thesis have an 
important bearing upon suggestions that have been put forward to explain some of the 
facts in the distribution both of the Mammals and of the Arthropods :— 
1. “The principal lines of migration in later geological epochs have been radial 
from Holarctic centres of dispersal.” (P. 172.) 
2. “The numerous hypothetical land-bridges in temperate, tropical, and southern 
regions, connecting continents now separated by deep oceans, which have 
been advocated by various authors, are improbable and unnecessary to 
explain geographic distribution. On the contrary, the known facts point 
distinctly to a general permanency of continental outlines during the later 
epochs of geologic time, provided that the allowance be made for the known 
or probable gaps in our knowledge.” (P. 173.) 
As regards the Mammalia, mentioned in this part of the ‘Biologia,’ whose distribution 
is tentatively assigned to vanished land-bridges, Mr. Matthew holds the following 
opinions. The resemblance between Thylacinus and the extinct South American 
Sparassodont Marsupials, believed by some American paleontologists to indicate close 
affinity, is held by Mr. Matthew to be adaptively convergent (p. 265); and Mr. Tate 
Regan has quite independently come to this conclusion (British Antarctic ‘Terra 
Nova’ Exped. 1910, Zoology, i. no. 1, pp. 41-438, 1914). 
Mr. Matthew thinks that the ancestors of the Australian Marsupials entered 
Australia by way of Southern Asia, while those of the South American forms came 
down from North America. Mr. Matthew ascribes the absence of fossil Marsupials 
from Asia to the “imperfection of the geological record,’ and does not discuss either 
their comparative paucity in the Austro-Malayan Islands or their absence to the 
west of Wallace’s Line—facts, which in my opinion suggest evolution in Australia, 
followed by northward migration into Austro-Malaya. Since the Didelphyide have 
survived in South America since the invasion of higher placental types, and have even 
successfully penetrated into North America, it seems to me that the disappearance of 
the Marsupials from Holarctica and their absence at the present time from Indo- 
Malaya can only be provisionally assigned to the unsuccessful competition with more 
