THE ARGUMENT FROM PALAEONTOLOGY 69 



the same group, and the first birds were pro- 

 bably smaller than Archzeopteryx. Reptiles and 

 mammals also show in their earlier and smaller 

 types more primitive features than their larger 

 descendants. 



Again, in the pedigree of the horse, one of the 

 most striking points is the progressive reduction in 

 size met with as we pass backwards in time. The 

 Pliocene Hipparion was smaller than the existing 

 horse ; the Miocene RIesohippits was about the size 

 of a sheep ; while the Eocene Eokipptis was no larger 

 than a fox. Not only is there good reason for 

 holding that, as a rule, larger animals are descended 

 from ancestors of smaller size, but there is also much 

 evidence to show that increase in size beyond certain 

 limits is disadvantageous, and may lead to destruc- 

 tion rather than to survival. It has happened 

 several times in the history of the world, and in 

 more than one group of animals, that gigantic stature 

 has been attained immediately before extinction of 

 the group, a final and tremendous effort to secure 

 survival, but a despairing and unsuccessful one. 

 The Ichthyosauri, Plesiosauri, and other extinct 

 reptilian groups, the Moas, and the huge extinct 

 Edentates, are well-known examples; to which 

 before long will be added the elephants and the 

 whales. 



The same classification applies to both recent and 

 fossil animals ; the large divisions are the same, but 

 many minor groups have become extinct. All 

 existing groups are not known to have existed for 

 all time, and many have certainly not done so. Still 



