The Homes and Migrations of the earliest 

 known Forms of Animal Life, as indicated 

 by Recent Researches.' 



THERE is no portion of the geological record more important to 

 the biologist than that which contains the history of the earliest 

 known forms of animal life, for whether he believes in the theory of 

 evolution or not, he is there made to see that there is a remarkable 

 similarity in the forms which constitute the earliest faunas wherever 

 they have been discovered. In speaking generally of these faunas 

 we do not, of course, mean that similar marine animals occurred in 

 each area at the same exact period in the world's history ; on the 

 contrary, if we admit that the animals migrated then as now when the 

 conditions were favourable or otherwise, such would be impossible ; 

 but what is meant is that they occupy in the geological succession 

 relatively the same general position. For instance, where the faunas, 

 which we may here call A, B, and C, are found in conformable 

 strata, the order of their appearance is the same in each area. If 

 the sections have been correctly interpreted, C has in no case been 

 found to precede A, nor B to succeed C. Year by year we have been 

 made acquainted with fresh discoveries among the older rocks, but 

 whether the evidence comes from Australia, China, India, Europe or 

 America the fact remains that the order of the appearance of certain 

 forms of animal life in the succession does not vary from that which 

 had previously been made out in other areas. In the most favoured 

 areas the rocks can only be expected to contain a very imperfect 

 history of the animal life which existed at the time when they were 

 deposited ; still, sufficient evidence has been obtained to make it easy 

 to realise what were the dominant forms prevailing at the time. For 

 instance, it is well known that the earliest faunas are everywhere 

 characterised by having Trilobites as their dominant organisms, and 

 further that each fauna is distinguished by well-recognised genera 

 with a comparatively limited vertical range. As the earliest faunas 

 of which we have any knowledge contain well-developed forms 

 belonging to widely separated groups, it is clear that we are here far 

 from the beginning of life on the globe. How is it then that, with all 



1 Read at the meeting of the British Association, Oxford, 1894. 



2 E 



