The essential difference between hand and foot is therefore not physiological, but _morphological_, and is determined by the characteristic structure of the bony skeleton and of the muscles attached to it. The ankle-bones differ from the wrist-bones in arrangement, and the foot possesses three special muscles not existing in the hand (a short flexor muscle, a short extensor muscle, and a long fibular muscle). In all these respects, Apes and Semi-apes entirely agree with man, and hence it was quite erroneous to separate him from them as a special order on account of the stronger differentiation of his hand and foot. It is the same also with all the other structural features by means of which it was attempted to distinguish Man from Apes; for example, the relative length of the limbs, the structure of the skull, of the brain, etc. In all these respects, without exception, the differences between Man and the higher Apes are less than the corresponding differences between the higher and the lower Apes. Hence Huxley, for reasons based on the most careful and most accurate anatomical comparisons, arrives at the extremely important conclusion—“Thus, whatever system of organs be studied, the comparison of their modifications in the Ape series leads to one and the same result, that the structural differences which separate Man from the Gorilla and Chimpanzee are not so great as those which separate the Gorilla from the lower Apes.” In accordance with this, Huxley, strictly following the demands of logic, classes Man, Apes, and Semi-apes in a single order, _Primates_, and divides it into the following seven families, which are of almost equal systematic value: (1) Anthropini (Man); (2) Catarrhini (genuine Apes of the Old World); (3) Platyrrhini (genuine American Apes); (4) Arctopitheci (American clawed Apes); (5) Lemurini (short-footed and long-footed Semi-apes, p. 255); (6) Chiromyini (p. 256); (7) Galeopithecini (Flying Lemurs, p. 256). SYSTEMATIC SURVEY _Of the Families and Genera of Apes._ -----------------+------------------------+---------------------+------------------ _Sections_ | _Families_ | _Genera_ | _Systematic Name_ _of_ | _of_ | _of_ | _of_ _Apes._ | _Apes._ | _Apes._ | _the Genera._ -----------------+------------------------+---------------------+------------------ I. APES OF THE NEW WORLD (+Hesperopitheci+), OR FLAT-NOSED APES (+Platyrrhini+). ----------------------------------------------------------------------------------- A. =Platyrrhini= { I. Silky apes { 1. Brush ape 1. Midas =with claws= { _Hapalida_ { 2. Lion ape 2. Jacchus { +Arctopitheci+ {