2i8 CONTINUITY. 



analogous phenomena ; it dives by the aid of its wings, and 

 is the only insect of the vast order it belongs to that is at all 

 aquatic. 



The discovery of the Eozoon is of the highest importance 

 in reference to the derivative hypothesis, occurring as it does 

 in strata that were formed at a period inconceivably antece- 

 dent to the presupposed introduction of life upon the globe, 

 and displacing the argument derived from the supposition 

 that at the dawn of life a multitude of beings of high .organi- 

 sation were simultaneously developed (in the Silurian and 

 Cambrian strata). 



Professor A. De Candolle, one of the most distinguished 

 Continental botanists, has, to some extent, abandoned the 

 tenets held in his ' Geographic Botanique,' and favours the 

 derivative hypothesis in his paper on the variation of oaks ; 

 following up a paper by Dr. Hooker, on the oaks of Palestine, 

 showing that some sixteen of them are derivative, he avows 

 his belief that two-thirds of the 300 species of this genus, 

 which he himself describes, are provisional only. 



Dr. Hooker, who had only partially accepted the derivative 

 hypothesis propounded before the publication of ' The Origin 

 of Species through Natural Selection/ at the same time de- 

 clining the doctrine of special creation, has since then cordially 

 adopted the former, and illustrated its principles by applying 

 them to the solution of various botanical questions : first, in 

 reference to the flora of Australia, the anomalies of which he 

 appears to explain satisfactorily by the application of these 

 principles ; and, latterly, in reference to the Arctic flora. 



In the case of the Arctic flora, he believes that originally 

 Scandinavian types were spread over the high northern lati- 

 tudes ; that these were driven southwards during the glacial 

 period, when many of them changed their forms in the struggle 

 that ensued with the displaced temperate plants ; that on the 

 returning warmth, the Scandinavian plants, whether changed 

 or not, were driven again northwards and up to the mountains 

 of the temperate latitudes, followed in both cases by series of 

 pre-existing plants of the temperate Alps. The result is the 

 present mixed Arctic flora, consisting of a basis of more or 

 less changed and unchanged Scandinavian plants, associated 



