104 SECULAR INCREASE IN SIZE CHAP, iv 



have left a dwarfish offspring ; that there were giants of 

 old, and that there is a puny race to-day. As a matter of 

 fact, the study of the gradual evolution of the early Tertiary 

 Mammalia into their descendants of later times shows very 

 plainly the truth of this interesting generalisation : That the 

 primitive types were all small creatures, and that in those 

 instances where we can trace a pedigree, there was a gradual 

 increase in size up to a point where greater increase led to 

 extinction. "We point out later on a number of facts illus- 

 trating this matter in detail. It has been ascertained, for 

 instance, that the pedigree of the Horses, the Camels, the Rhino- 

 ceroses, and many other groups, commences with small forms 

 and culminates in large ones. It may be urged that such 

 animals as the Tapir are to-day smallish forms, and that related 

 to them in the past were the gigantic Titanotheres ; but in this 

 and similar cases it will be found that the extinct giants were 

 not in the direct line of pedigree, but represented side-branches 

 which waxed huge on their own account and then disappeared. 



