THE LIVING WORLD. 



vance and stationary condition as we have seen in 

 the animal world taken as a whole. This difference 

 is certainly a striking one, as we take a cursory 

 glance at the fossil study of plants and animals as 

 they are known to-day. The fact may, however, be 

 partly due to our incomplete knowledge of the lower 

 orders of plants. The lowest classes of plants are 

 almost wholly unrepresented by fossils, and through 

 all the geological ages it is the higher classes which 

 have been most preserved and most studied. Per- 

 haps if our fossil record of lower plants were as com- 

 plete as that of the lower animals, we should find 

 that here too there has been divergence from com- 

 mon centres to a much greater extent than now 

 appears. But however that may be, the facts as 

 collected at the present time point to a history of 

 much more continuous progression among plants 

 than animals. See Fig. 21. 



