T. Bland on the Geographical Distribution of Molhisca. 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 

 Divine 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, j p. 145. 



"However active physical agents maybe, it would be very 

 unphilosophical to consider them as the source or origin of the 

 beings 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- 

 servation." — Lake Superior, p. 142. 



May we not fairly remark, that Lyell, Forbes, Darwin, and 

 other writers, overlookmg the theory, that the existing species 

 were introduced by the creation of many individuals, have been 

 often driven to forced constructions, and applications of the effects 

 of physical agents, to support their views as to the unity of the 

 origin of species, and other opinions. 



Dr. Binney adopted the theory of several distinct centres or 

 foci from which species radiated, and, in his work already cited, 

 remarks that the axiom in the philosophy of zoology, that dis- 

 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, 

 the same species may have been created at different centres. In this 

 way the presence of species in every part of the earlh may be ac- 

 counted for, and thus only can we satisfactorily explain the diffusion 

 of the species that have been under consideration." — Vol. I, p. 148. 



Prof. Agassiz in a paper on the " Geographical distribution of 

 Animals," in the Chi^istian Examiner, {Boston, March, 1850,) ex- 

 amines, in a masterly manner, the question of the plurality of origin 

 of species. 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 natii- 



