bw: Li « c 
Geographical Distribution of Crustacea. 45 
XIII. 'There is evidence in the exceedingly small number of 
"'T'orrid zone species identical in the Atlantic and Indian Oceans, 
that there has been no water communication across from one to 
the other in the 'T'orrid zone, during the period since existing 
species of Crustacea were first on the globe. 
XIV. As to zoological centres of diffusion for groups of spe- 
cies, we can point out none. Each species of Crustacea may 
have had its place of origin and single centre of diffusion in 
many and perhaps the majority of cases. But we have no rea- 
son to say that certain regions were without life, and were peo- 
pled by migration from specific centres specially selected for this 
end. 1f such centres had an existence, there is at present no 
means by which they may be ascertained. "The particular tem- 
perature region in which a species originated may be ascertained 
by observing which is most favorable to its development: we 
should thus conclude that the F'anzna dentata, for example, was 
created in the subtorrid region and not the torrid, as it attains its 
largest size in the latter. By pursuing this course with reference 
to each species, we may find some that are especially fitted for 
almost every different locality. Hence, we might show, as far 
as reason and observation can do it, that all regions have had 
their own special creations. 
The world throughout all its epochs in past history, has been 
furnished with life in accordance with the. times and seasons, 
each pos being adapted to its age, its place, and its fellow spe- 
cies of life.* *. . 
* The abstracts in the American Journal of Science from the "up Boflert 
relating to the Geographical Distribution of Crustacea, which are here concluded, 
are contained in volumes xvi, xviii, xix and xx. The map illustrating the subject of 
Oceanic temperature, the Zones and Zoological Provinces, is in volume xvi. 
