Heal Affinities in the Animal Kingdom, 21 



facts, both zoological and geological, which have of late been 

 most carefully studied ; for the agreement between the zoo- 

 logical affinities and the geological division of types in the 

 series of formations is so striking, especially in certain 

 classes which have of late been the object of particular study, 

 that I think it may now be laid down as a fact, that sytema- 

 tic classifications which are not, at the same time, the ex- 

 pression of the succession of families in the order of time, 

 can no longer be considered as expressing the real affinities 

 existing among the animals which they embrace. The most 

 fortunate approximations which naturalists have attempted 

 at different epochs, have really received a striking confirma- 

 tion by modern palaeontological discoveries, and that often 

 when those to whom we owe them were unconscious of it. 

 These results are so striking, that even now, in some classes 

 of animals, the knowledge of fossils, and their order of suc- 

 cession, may serve us as a guide to correct the zoological 

 system, just as, on the other hand, the advanced state of our 

 anatomical knowledge will lead us to a correct determination 

 of the geological age of certain deposits, even although v, e 

 should not discover in them any fossil species identical with 

 those of well-determined formations of the same era. I shall 

 even go further, for I can now foresee the time when these 

 results will equally harmonise with the laws of the geogra- 

 phical distribution of animals on the surface of the globe ; 

 but the facts relating to this order of connection are not yet 

 sufficiently known to induce me to enter upon the considera- 

 tion of them on this occasion. 



The most important result of modern palaeontological re- 

 searches, in reference to the present question, is the fact, no 

 longer open to dispute, of the simultaneous appearance of 

 particular types of all classes of invertebrate animals, from 

 the most ancient periods of the development of life on the 

 surface of the globe. We find, in fact, in the palaeozoic forma- 

 tions, the fossil remains of radiata, mollusca, and articulata. 

 We may even admit that the first representatives of all the 

 classes of the three great branches are contemporaneous, for 

 we find Polypes, Echinoderma, Acephala, Gasteropods,Cepha- 

 lopods, and Testaceous and Crustaceous Vermes, in the most 



