22. Stage of _Simiæ_. Orbit completely separated from the temporal fossa by an inward extension of the frontal and malar bones meeting the alisphenoid. Placenta consolidated into a disc, and with a maternal deciduous portion. Mammæ pectoral only. The dental formula is 2.1.3.3. All the fingers and toes are protected by flat nails. The tail is long. The American prehensile-tailed monkeys are a lower side-branch. 23. Stage of _Catarrhinæ Cercopithecidæ_. The dental formula is 2.1.2.3, owing to the loss of one pair of premolars in each jaw. The frontal and alisphenoid bones are in contact, separating the parietal from the malar bone; this feature is correlated with the enlarged brain. The internarial septum is narrow, and the nostrils look forwards and downwards instead of sidewards--hence the term 'Catarrhinæ.' The external auditory meatus is long and bony. The tail is long, with the exception of _Macacus inuus_. The body is covered with a thick coat of furry hair. Catarrhine monkeys have existed, we know with certainty, since the Miocene. 24. Stage of _Catarrhinæ Anthropoidæ_, or _Apes_. Now represented by the large apes--namely, the Hylobates or gibbon of South-Eastern Asia, _Simia satyrus_, the orang-utan of Sumatra and Borneo, _Troglodytes gorilla_, _T. niger_ and _T. calvus_, the gorilla and the chimpanzees from Western Equatorial Africa. Of fossils are to be mentioned Pliopithecus and Dryopithecus from European Miocene, and _Troglodytes sivalensis_ from the Pliocene of the Punjaub. The tail is reduced to a few caudal vertebræ, which are transformed into a coccyx, not visible externally; but in the embryos of apes and man the tail is still a conspicuous feature. The walk is semierect; in adaptation to the prevailing arboreal life, the arms are longer than the legs. The hair of the body is considerably more scanty than in the tailed monkeys. _Troglodytes calvus_, a species or variety of chimpanzee, is bald-headed. None of the recent genera of apes can lay claim to a place in the ancestry of mankind. 25. Stage of _Pithecanthropi_. Hitherto the only known representative is _Pithecanthropus erectus_, from the Upper Pliocene of Java. In adaptation to a more erect gait, the legs have become stronger and the hind-hand has been turned into a flat-soled walking 'foot.' The brain is considerably enlarged. Presumably it is still devoid of so-called articulate speech; this is indicated by the fact that children have to learn the language of their parents, and by the circumstance that comparative philology declares it impossible to reduce the chief human languages to anything like one common origin. 26. _Man._ Known with certainty to have existed as an implement-using creature in the last Glacial epoch. His probable origin cannot, therefore, have been later than the beginning of the Plistocene. The place of origin was probably somewhere in Southern Asia.