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His object at the present time was not to explain the origin 

 and connection of faunas ; we must take them as we find them, as 

 matters of fact, without reference now as to how they were pro- 

 duced. It is important in the discussion of this subject to bear in 

 mind that some faume are strictly defined, while others run to- 

 gether ; there is very great difference in this respect ; Mr. Wal- 

 lace, a strong advocate of Darwin's theory, admits the remarkable 

 limitation between the Australian and Indian Archipelago fauna;, 

 separated by a strait only fifteen miles wide, yet, with the excep- 

 tion of a few birds, entirely distinct. Faunce are not necessarily, 

 therefore, like each other because near together, nor unlike be- 

 cause widely separated ; the former is shown by the case just 

 cited, in which there is complete distinction, though circumstances 

 favor a mingling of faunas ; on the other hand, those of widely 

 distant Africa and the east coast of America between the tropics 

 are very much alike. These do not look like migrations, which 

 are at best limited, and in which, if the conditions of life were 

 much changed, the animals would be destroyed ; marine animals, 

 in an element which invites miorration, are verv much circum- 

 scribed within limits as to depth of water, and could not migrate 

 from one part of the world to another across ocean abysses. An- 

 other obstacle in the way of migration is the transfer of progeny ; 

 eggs in most animals cannot bear much change of temperature or 

 of location, without destruction of the contained embryo. He 

 would pursue a strictly zoological method, as in the comparison 

 of living animals. Without discrediting the researches of others, 

 he would simply examine their materials anew, with a new object 

 in view ; the usual investigations are too general and unsatisfac- 

 tory, and their results not precise enough for use in the question 

 of the origin and limits of species ; the materials were not accu- 

 mulated for this purpose, but for zoological questions in which 

 identity, overlooking slight differences in species, might be as- 

 sumed without leading to grave errors, and without sufficient 

 examination. For instance, the animals of Europe and America, 

 once considered identical, are now admitted to be different species 

 on direct comparison. This is a purely zoological question ; the 

 older geological divisions are not coincident with zoological divis- 

 ions and faunte. In the carboniferous age, reptiles were the 

 highest vertebrates. As to the limit between reptiles and fishes, 



