T. Bland on the Geographical Distribution of Mollusca. 403 
been created in succession, at such times, and in such places as to 
enable them to multiply and endure for an appointed period, and 
occupy an appointed space on the globe.” p. 642. 
_ We see in the writings of these authors a constant recurrence 
to physical agents, as the sole cause of the distribution of the 
individuals of a species,—no suggestion that the contemporane- 
ous introduction of several original individuals was part of the 
ivine plan of the Creator. ‘There will be no scientific evi- 
dence of God’s working in nature,” says Professor Agassiz, “ until 
naturalists have shown that the whole creation is the expression 
of a thought, and not the product of physical agents.”—Lake 
Superior, (Boston, 1850,) p. 145. 
“However active physical agents may be, it would be very 
unphilosophical to consider them as the source or origin of the 
eings upon which they show so extensive an influence. Mis- 
taking the circumstantial relation under which they appear, for a 
causal connection, has done great mischief in natural science, and 
led many to believe they understood the process of creation, be- 
cause they could account for some of the phenomena under ob- 
tinct zoological regions exist, has been greatly fortified by it. 
_ After reasoning on the subject, he adds :—“ Having thus adopted 
the theory of distinct zoological centres, and admitting that as suc- 
cessive portions of the earth’s surface emerged from the waters, and 
became adapted to sustain the different classes of animals, those 
races which were fitted for the then physical condition of things, 
Were brought into being by the prolific hand of nature, we find no 
difficulty in supposing that under the same or similar conditions, 
same species may have been created at different centres. In this 
Way the presence of species in every part of the earth — 
counted for, and thus only can we satisfactorily explain the diffusion 
of the species that have been under consideration.’ —Vol. I, p. 148. 
rof. Agassiz in a paper on the “ Geographical distribution of 
Animals,” in the Christian Examiner, ( Boston, March, ne ce 
amines, in a masterly manner, the question of the plurality of origin 
ies. The following is his view of the natural distribution 
of animals ;—* that they originated primitively over the whole ex- 
tent of their natural distribution ; that they originated there, not in 
pairs, but in large numbers, in such proportions as suits their natu- 
