the Geographical Distribution of Marine Species. 323 
terior of the ocean is raised four to five degrees in temperature 
above the normal grade, by the same waters spreading eastward ; 
and between Great Britain and Iceland, the temperature is at least 
ten degrees warmer than in the corresponding latitude of the 
South Pacific, aud thirteen or fourteen degrees warmer than in 
the same latitude in the South Atlantic. 
he influence of so warm an ocean on the temperature of 
Britain, and on its living productions, animal and vegetable, is ap- 
parent, when it is considered, that the winds take the tempera- 
ture nearly of the waters they pass over. And the effects on the 
same region, that would result from deflecting the Gulf Stream in 
some other direction, as brought out by Prof. Hopkinst and others, 
and substituting in the Northern Atlantic the temperature of the 
Southern Atlantic, is also obvious, without further illustration. 
The discussion of these subjects would be foreign to the topic 
before us 
The subdivision of the oceans into Temperature Regions, af- 
fords a convenient means of dividing off the coasts into Zoologica 
Provinces. A comparison of the facts afforded by the distribution 
of Crustacea, with the positions and extent of the Provinces thus 
deduced, show that they are natural, and may in general be well 
characterized. 
Zoological Provinces have been considered by some as centres 
of creation, and therefore of diffusion, for groups of species. But 
such kinds of centres we fail to distinguish in any part of the 
globe. Each species may have had its one point of origin and 
single centre of diffusion, in many, and perhaps the majority of 
cases: but, however the fact may be, we have no evidence for as- 
serting that particular regions were without life, and were peopled 
by migration from specific and predetermined centres ; for if there 
were such centres of diffusion, there are at present no means by 
* Ross, in his Antarctic Voyage, found the sea-temperature in 60° south and 3° 
west, 314° F., in the month of March; at the South Shetlands, 61° south, the po 
temperature was 31° to 35° in January (midsummer) ; and in the same latitude, an 
45° west, it was 30°1° in bis? : = 
+ Quarterly Jour. Geol. Soc. vol. viii., p. 56, and Amer. Jour. Sci, 1853, vol. Xv. 
