1878.] 
Notices of Books . 
419 
ground unless these peculiar methods are adopted which have 
now been invented.” The bearing of this discovery upon the 
question of spontaneous generation will at once be recognised. 
Bulletin of the United States Geological and Geographical Survey 
of the Territories. Vol. iv., No. 2. Washington: Govern- 
ment Printing-Office. 
This issue includes an Essay which in point of importance, if 
not of extent, is well worthy to figure as an independent work. 
Under the tirle “ The Geographical Distribution of the Mammalia 
considered in relation to the Principal Ontological Regions of the 
Earth, and the Laws that Govern the Distribution of Animal 
Life,” Mr. J. A. Allen criticises the views of Dr. Sclater and Mr. 
A. R. Wallace,* and expounds in detail a system of his own, of 
which he published a preliminary notice in 1871, and to which 
Mr. Wallace refers in his great work. His fundamental principle 
is that “ life is distributed in circumpolar zones under the control- 
ling influence of climate, and mainly of temperature.” Quoting 
from Mr. Wallace the declaration that “ the continents, resem- 
bling a huge creeping plant with roots at the North Pole, and the 
matted stems and branches of which cover a large part of the 
northern hemisphere and send three great offshoots toward the 
South Pole,” he likens the distribution of animal life to that of 
the land. Near the North Pole the land is comparatively little 
interrupted, the Eastern and Western Worlds being sundered 
merely by Behring’s Straits. In harmony with this geographical 
faCt we have an Ardfic or North Circumpolar realm of animal 
life whose essential forms are common to the two continents. 
The further we proceed from the Pole the more we find differenti- 
ation increase. Thus Mr. Allen obtains eight primary divisions 
or “ realms ” — the Ardfic, the North Temperate, the American 
Tropical, the Indo-African, the South American Temperate, The 
Australian, the Lemurian, and the Antarctic. Most of these 
realms are subdivided into “ regions,” and again into “ provinces.” 
The resulting arrangement differs, however, from that of Mr. 
Wallace less perhaps than might have been at first sight ex- 
pected, and the same boundary lines are observed in both. Thus, 
setting the Circumpolar realm aside, Mr. Allen’s North Temperate 
— with its two secondary divisions — coincides with Mr. Wallace’s 
NearCtic and PalasarCtic regions. The American Tropical of the 
one author and the Neotropical of the other differ merely in the 
circumstance that Mr. Allen has raised its extreme southern por- 
tion to the rank of a distinCt primary division. The Ethiopian 
* See Geographical Distribution of Animals, by A. R. Wallace. 
