320 Geographical Distribution of Animals 
this anatomist dealt with some of the fundamental causes of distri- 
bution. 
Whilst Tiedemann restricted himself to Birds, A. Desmoulins in 
1822 wrote a short but most suggestive paper on the Vertebrata, 
omitting the birds; he combated the view recently proposed by the 
entomologist Latreille that temperature was the main factor in distri- 
bution. Some of his ten main conclusions show a peculiar mixture 
of evolutionary ideas coupled with the conception of the stability of 
species : whilst each species must have started from but one creative 
centre, there may be several “analogous centres of creation” so far 
as genera and families are concerned. Countries with different 
faunas, but lying within the same climatic zones, are proof of the 
effective and permanent existence of barriers preventing an exchange 
between the original creative centres. 
The first book dealing with the “geography and classification” of 
the whole animal kingdom was written by W. Swainson! in 1835. He 
saw in the five races of Man the clue to the mapping of the world 
into as many “true zoological divisions,’ and he reconciled the five 
continents with his mystical quinary circles. 
Lyell’s Principles of Geology should have marked a new epoch, 
since in his Elements he treats of the past history of the globe and 
the distribution of animals in time, and in his Principles of their 
distribution in space in connection with the actual changes undergone 
by the surface of the world. But as the sub-title of his great work 
“Modern changes of the Earth and its inhabitants” indicates, he 
restricted himself to comparatively minor changes, and, emphatically 
believing in the permanency of the great oceans, his numerous and 
careful interpretations of the effect of the geological changes upon 
the dispersal of animals did after all advance the problem but 
little. 
Hitherto the marine faunas had been neglected. This was 
remedied by E. Forbes, who established nine homozoic zones, based 
mainly on the study of the mollusca, the determining factors being 
to a great extent the isotherms of the sea, whilst the 25 provinces 
were given by the configuration of the land. -He was followed by 
J. D. Dana, who, taking principally the Crustacea as a basis, and 
as leading factors the mean temperatures of the coldest and of the 
warmest months, established five latitudinal zones. By using these 
as divisors into an American, Afro-Kuropean, Oriental, Arctic and 
Antarctic realm, most of which were limited by an eastern and 
western land-boundary, he arrived at about threescore provinces. 
1 «A Treatise on the Geography and Classification of Animals,” Lardner’s Cabinet 
Cyclopaedia. London, 1835. 
