326 THE INDUCTIONS OF BIOLOGY. 



original type. That which Prof. Huxley's argument proves, 

 and that only which he considers it to prove, is that organisms 

 have no innate tendencies to assume higher forms, and that 

 " any admissible hypothesis of progressive modification, must 

 be compatible with persistence without progression through 

 indefinite periods." 



One very significant fact must be added, concerning the 

 relation between distribution in Time and distribution in 

 Space. I quote it from Mr Darwin : " Mr Clift many years 

 ago showed that the fossil mammals from the Australian 

 caves were closely allied to the living marsupals of that con- 

 tinent. In South America, a similar relationship is manifest ^ 

 even to an uneducated eye, in the gigantic pieces of armour 

 like those of the armadillo, found in several parts of La Plata ; 

 and Professor Owen has shown in the most striking manner 

 that most of the fossil mammals, buried there in such num- 

 bers, are related to the South American types. This relation- 

 ship is even more clearly seen in the wonderful collection of 

 fossil bones made by MM. Lund and Clausen in the caves of 

 Brazil. I was so much impressed with these facts that I 

 strongly insisted, in 1839 and 1845, on this ' law of the suc- 

 cession of types,' on ' this wonderful relationship in the 

 same continent between the dead and the living.' Professor 

 Owen has subsequently extended the same generalization to the 

 mammals of the Old World. We see the same law in this 

 author's restorations of the extinct and gigantic birds of New 

 Zealand. We see it also in the birds of the caves of Brazil. 

 Mr Woodward has shown that the same law holds good, with 

 sea-shells, but from the wide distribution of most genera of 

 molluscs, it js not well displayed by them. Other cases could 

 be added, as the relation between the extinct and living land- 

 shells of Madeira ; and between the extinct and living brack- 

 ish-water shells of the Aralo-Caspian Sea.'" 



The general results then, are these. Our knowledge of 

 distribution in Time, being derived wholly from the evidence 

 afforded by fossils, is limited to that geologic time of which 



