152 Professor Huxley, [June 3, 



a long series of states very different from that which we now know, and 

 whose succession occupied pre-geological time. 



The doctrine of physical uniformity and that of physical progression 

 are therefore perfectly consistent, if we regard geological time as having 

 the same relation to pre-geological time as historical time has to it. 



The accepted doctrines of palaeontology are by no means in 

 harmony with these tendencies of physical geology. It is generally 

 believed that there is a vast contrast between the ancient and the 

 modern organic worlds — it is incessantly assumed that we are acquainted 

 with the beginning of life, and with the primal manifestation of each of 

 its typical forms : nor does the fact that the discoveries of every year 

 oblige the holders of these views to change their ground, appear sensibly 

 to affect the tenacity of their adhesion. 



Without at all denying the considerable positive differences which 

 really exist between the ancient and the modern forms of life, and 

 leaving the negative ones to be met by the other lines of argument, an 

 impartial examination of the facts revealed by palaeontology seems to 

 show that these differences and contrasts have been greatly exaggerated. 



Thus, of some two hundred known orders of plants, not one is 

 exclusively fossil. Among animals, there is not a single totally extinct 

 class ; and of the orders, at the outside not more than seven per cent, 

 are unrepresented in the existing creation. 



Again, certain well marked forms of living beings have existed 

 through enormous epochs, surviving not only the changes of physical 

 conditions, but persisting comparatively unaltered, while other forms 

 of life have appeared and disappeared. Such forms may be termed 

 " persistent types" of life ; and examples of them are abundant enough 

 in both the animal and the vegetable worlds. 



Among plants, for instance, ferns, club mosses, and ConifercB, some 

 of them apparently generically identical with those now living, are 

 met with as far back as the carboniferous epoch ; the cone of the oolitic 

 Araucaria is hardly distinguishable from that of existing species ; a 

 species of Pinus has been discovered in the Purbecks, and a walnut 

 {Juglans) in the cretaceous rocks.* All these are types of vegetable 

 structure, abounding at the present day ; and surely it is a most 

 remarkable fact to find them persisting with so little change through 

 such vast epochs. 



Every subkingdom of animals yields instances of the same kind. 

 The Glohigerina of the Atlantic soundings is identical with the cre- 

 taceous species of the same genus ; and the casts of lower Silurian 

 Foraminifera, recently described by ^ Ehrenberg, assure us of the 

 very close resemblance between the oldest and the newest forms of 

 many of the Protozoa. 



Among the Coelenferata, the tabulate corals of the Silurian epoch 

 are wonderfully like the millepores of our own seas, as every one may 

 convince himself who compares Heliolites with Heliopora. 



** I state these facts on the authority of my friend Dr. Hooker. — T. H. H. 



