GEOLOGICAL SUCCESSION 291 



America or in Australia, the most skilful naturalist 

 would hardly be able to say whether the existing or the 

 pleistocene inhabitants of Europe resembled most closely 

 those of the southern hemisphere. So, again, several 

 highly competent observers believe that the existing 

 productions of the United States are more closely related 

 to those which lived in Europe during certain later 

 tertiary stages, than to those which now live here ; 

 and if this be so, it is evident that fossiliferous beds 

 deposited at the present day on the shores of North 

 America would hereafter be liable to be classed with 

 somewhat older European beds. Nevertheless, looking 

 to a remotely future epoch, there can, I think, be little 

 doubt that all the more modern marine formations, 

 namely, the upper pliocene, the pleistocene and strictly 

 modern beds, of Europe, North and South America, and 

 Australia, from containing fossil remains in some degree 

 allied, and from not including those forms which are 

 only found in the older underlying deposits, would be 

 correctly ranked as simultaneous in a geological sense. 

 The fact of the forms of life changing simultaneously, 

 in the above large sense, at distant parts of the world, 

 has greatly struck those admirable observers, MM. 

 de Verneuil and d'Archiac. After referring to the 

 parallelism of the palaeozoic forms of life in various 

 parts of Europe, they add, ' If struck by this strange 

 sequence, we turn our attention to North America, and 

 there discover a series of analogous phenomena, it will 

 appear certain that all these modifications of species, 

 their extinction, and the introduction of new ones, 

 cannot be owing to mere changes in marine currents 

 or other causes more or less local and temporary, but 

 depend on general laws which govern the whole animal 

 kingdom.' M. Barrande has made forcible remarks to 

 precisely the same effect. It is, indeed, quite futile to 

 look to changes of currents, climate, or other physical 

 conditions, as the cause of these great mutations in the 

 forms of life throughout the world, under the most dif- 

 ferent climates. We must, as Barrande has remarked, 

 look to some special law. We shall see this more clearly 



