4bO Geological Society. 



mature, or senile position of the particular animals in the evolving 

 series to which they belong. 



Hitherto there seems to be only (»ne case in which we have 

 enough materials for forming a judgment as to whether a funda- 

 mental advance may occur more than once. Mammal-like reptiles 

 are abundant in the Permian of Xorth America and in the Permian 

 and Trias of South Africa and other parts of the Old World. 

 Recent studies have shown that all specializations in the North- 

 American forms are in the direction of higher reptiles, while 

 all those in the South African forms are in the direction of 

 mammals. Hence, although there is evidence of two possible 

 sources of mammals, only one appears to have produced them. 



Among advances of lower degree, the origin of the monkeys or 

 lower Anthropoidea may be considered. It is agreed that they 

 arose from the Lemm'oidea w-hich were almost universally 

 distributed over the great continents at the beginning of the 

 Tertiary Era. They seem to have evolved separately in America 

 and in the Old World, but the two series are very sharply 

 distinguished, although they form one zoological 'suborder.' When 

 isolated on the island of Madagascar, some of the same animals 

 aciju-rcd a few peculiarities of the American, others of the Old World 

 Anthropoidea, but never really advanced beyond the Lemuroid 

 stage, merely becoming senile just before their extinction. Hence, 

 the Lemuroidea evolved in three different ways, and the resulting 

 grovips are very easily distinguished. 



The study of the Tertiary Ungulata is especlall}' important, 

 because most of the groups arose either in North America or in 

 the Old World, Avhieh were imited and separated several times. 

 It seems clear that, although each group probably originated bvit 

 once in one particular area, its members soon diverged into several 

 independently evolving series, each imbued with some definite 

 impulse or momentum towards specialization in the same w-ay in 

 the course of geological time, only at different rates. There were 

 thus, for example, several distinct lines of horses and rhinoceroses, 

 but all from the same source. 



It is now well known that the characteristic South American 

 Tertiary Ungulates arose in an isolated area, and many of their 

 specializations are curiously similar to some of those observed 

 among European Eocene and Oligocene Ungulata which soon 

 proved abortive or ' inadaptive.' They are, however, by no means 

 identical. 



While so many changes have occun-ed during the evolution of 

 the vertebrates, the persistence of characters and the strength 

 of heredity in numerous cases are still as perplexing as they were 

 when Huxley first directed special attention to * persistent types.' 

 The President enumerated some illustrations. 



