AND AFFIXITIES OF TARSIITS. 475 



a Still earlier period, i. e. there were real monkeys in the Eocene. 

 I do not suppose that anyone will refuse to admit the certainty 

 of the derivation of the tailless Anthropomorpha from tailed 

 Catarhines; but the early development of true Simiidee shows 

 that the differentiation of the Old-World Apes into Cerco- 

 pithecida^ and Simiidae must have occurred almost immediately 

 after the Catarhines themselves came into being. 



Anyone who conscientiously investigates the anatom}' of the 

 Platyrrhine Apes, and attempts to interpret the vastly com- 

 plicated series of cerebral transformations that weie necessar}?^ to 

 convert a Tarsioid into a monkey, must be forced to admit that 

 this did not happen twice, but that the Platyrrhines and the 

 Catarhines were derived from a common stock, some archaic Ape 

 more primitive and more Tarsioid even than Parapithecus, and at 

 a time long before the close of the Eocene period. The history 

 of the ancestors of the, Anthropoidea thus becomes cleai-. 



In North Amei-ica (which was clearly the home of the Order 

 Primates) the Lemuroidea. and the Tarsioidea were differentiated 

 fi'om the ancestral Pi-imate probably at the close of the Creta- 

 ceous period. At some time during the Eocene (and somewhere 

 in the neigiibourhood of Araericfi) true monkeys were differ- 

 entiated from one of the Tarsioid groups. Some of these found 

 an asylum in South Ameiica and became specialised as the 

 Platyrrhines. But others (in Eocene times) made their way 

 to the Old World along with the Adapid and Anaptomorphid 

 ancestors of the Lemuroidea and Tarsioidea respectively. During 

 this migration these primiti\'e monkeys became transformed into 

 Catarhines, and the i-emains of Parcq^ithecus pi'ovide the evidence 

 of their reality and give ;\. hint as to their size and distinctive 

 features. 



There is one other aspect of the problem under discussion 

 which has been fruitful of much misunderstanding. The 

 Lemuroidea represent a, lower stratum of Primate evolution 

 than the Tarsioidea, just as the latter are on a very much lower 

 plane than the Anthropoidea. But, while the Lemuroidea retain 

 many features of brain, skull, face, placentation, et cetera, which 

 are survivals from their Pal eocene or Cretaceous ancestry — the 

 earliest Primates, — during the long span of time that has elapsed 

 since the Cretaceous period they have acquired a host of minor 

 specialisations of structure which have modified or masked much 

 of their original likeness to the other Primates. Tarsius, 

 however, although on a distinctly higher plane of Primate 

 development, has managed to escape extinction with fewer and 

 slighter specialisations than the Lemurs. Hence it has retained 

 a much more generalised and obviously primitive structure along 

 with the e'Pi'ms of the features that aie distinctive of monkevs. 



