234 Recent Literature. [ April, 
almost wholly. When, however, we come to the zodlogical subregions, 
temperature and mountain barriers, rivers and deserts are factors for the 
most part, though not always duly recognized in this work, for climatic 
causes are, we think, not given sufficient prominence, and the corre- 
spondence between zones of temperatures, and the distribution of faune 
are too lightly discussed. For example, he rejects the idea of an arctic 
region with a circumpolar fauna, contrary to the well-founded views of 
Agassiz, Dana, Huxley, and others, though he gives some good reason 
for his own opinion. Mr. Wallace’s six regions are those originally pro- 
posed by Sclater, namely, the Palearctic, Ethiopian, Indian, Australian, 
Neotropical, and Nearctic. 
Mr. Wallace disbelieves in the existence of an antarctic region, and we 
should be inclined to agree with him, but we see no good reason, if we 
are to confine ourselves to existing facts of distribution, for ignoring a 
seventh arctic region embracing all of America, Europe, and Asia north 
of the isothermal of 32°. We should follow Agassiz (1847) and others, 
as well as Huxley (1868) and put the northern limits of the Palwaretic 
and Nearctic regions, or Europe, Asia, and North America, respectively, 
south of the isothermal of 32°. In this case, we think, Mr. Wallace treats 
too lightly the importance of temperature in limiting zoégeographical re- 
gions, and is disposed to rely too strongly on the fact that this arctic region 
had in former times a warm climate, and supported a flora and fauna 
like that of north temperate Europe, Asia, and America. But the Glacial 
epoch destroyed the continuity of climate, and at the present time temper- 
ature is the prime factor in limiting life as regards this region of the 
globe. When we turn to the distribution of marine invertebrate life, a 
subject almost wholly ignored by Mr. Wallace, the extension into the 
arctic zone of Mr. Sclater’s Nearctic and Palearctic regions is entirely 
arbitrary. All the facts brought out by deep-sea researches and Scandi- 
navian, British, and American marine zodlogists tend to prove most 
forcibly that there is a circumpolar fauna, no more European-Asiatic 
than American,! and that this fauna may, at great depths, where the 
temperature of the water is the same (as it actually is), extend to Cuba 
and underlie the tropical zone of life. In fact, the fauna of the sea 15 
primarily polar or frigid, and tropical, and we believe that Messrs. Scla- 
ter and Wallace are quite wrong in ignoring the fact that even land 
animals share largely in this distribution. Indeed, in discussing the ~~ 
tribution of marine life, temperature is the main element in the limita- 
tion of zoölogical regions and subregions, as first shown by 2 — 
. D. Dana in 1853, in his essay on the geographical distribution © 
Crustacea, and again and again proved by marine zoologists and the 
results of the explorations by the United States Coast Survey, by Scan- 
1 Since the publication of Mr. Wallace’s work, in the Reports of the Valorous 
Expedition to Greenland, Mr. Jeffreys argues against and Mr. Norman in favor 
the Greenland marine fauna being American rather than European. 
