io8 DISCRIMINATIONS CHAP. 



this is no solution, but only a banish- 

 ment of the difficulty to some other 

 place. The more common bolt-hole for 

 escaping from this difficulty is to plead 

 the " imperfection of the record." But 

 this does not really avail us much. As 

 regards terrestrial forms of life, indeed, 

 it is true that the record is very imper- 

 fect, because the conditions are rare and 

 partial under which land animals can be 

 preserved in aqueous deposits. Conse- 

 quently, as regards them, we never get 

 a complete series. But there are many 

 great rock -formations of marine origin, 

 which were continuous deposits for ages, 

 at least long enough to embrace the 

 first appearance of many new species. 

 Yet these new species never seem to 

 be mere haphazard variations from pre- 

 existing forms. They never have the 

 least appearance of the lawless mixtures 

 of hybridism. On the contrary, the 



