eta See 
Geographical Distribution of Crustacea. 359 
stances surrounding it to be as intimate nearly as cause and effect. 
The Creator has, in infinite skill, adapted each species to its place, 
and the whole into a system of admirable harmony and perfection. 
In His wisdom, any difference of physical condition and kind of 
food at hand, is sufficient to require some modification of the in- 
timate structure of species, and this difference is expressed in 
the form of the body or members, so as to — an exac sine : 
of adaptation, which we are far from fully perceiving or ¢ mpre- 
hending with Hd present knowledge of the relations of nope 
to their habita 
When sna we find the same species in regions of unlike 
physical character, as, for example, in the seas of the Canaries 
and Great Britain—regions physically so unlike—we have strong 
reason for attributing the diffusion of the species migration. 
The difference between the Mediterranean and Great Britain 
created independently in the two could have been identical, or 
even have had that resemblance that exists between varieties; 
for this resemblance is usually of the most trivial kind, and affects 
only the least essential of the parts of a species. 
The continental species of Crustacea from the interior of dif- 
ferent continents, are not in any case known to be identical; and 
it is well understood that the zoological provinces angdistriets of 
the land are of far more limited extent than thos ocean 
The physical differences of the former are far more sting than 
those of the latter. As we have observed elsewhere, t 
ties of climate are greater; the elevation above the sea may wee! 
widely ; and numberless are the diversities of soil and its condi- 
tions, and the circumstances above and within it. Hence, as the 
creation of each species has had reference most intimately . pao 
and all of these conditions, as well as to other prospective ends, an 
identity between distant continental regions is seldom to be found, 
Comparatively few genera of Insects have as wide a range as those 
of Crustacea; and species with rare exceptions, have very narrow 
limits. Where the range of a species in this class is great, we 
ina on; but 
= bisa studied tae ‘abs is admitted as the true expla- 
nation. 
Throughout the warmer tropical oceans, a resemblance in the 
physical conditions of distant provinces is far more common and 
more exact than in the Temperate zone. And hence it would 
seem that we could not safely appeal to actual differences as an ar- 
gument against the creation of a species in more than one place in 
the tropics. The species spread over the Oriental Torrid zone 
