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Show 1873.] MR. ST. G. MIVART ON THE LEMURS. 509 tendency of the Simiadee to develop cheek-pouches and ischiatic callosities, and the constant absence of any manifestation of such tendencies in the Cebidae; (5) the different general form and habit which the two groups present. All these characters taken together seem to m e to make it highly probable that the Cebidce and Simiadae are no diverging offshoots from some common Ape-parent, but that they have arisen in an independence as complete as that between the origin of either of them and the origin of the Lemuroids or Carnivores. I need hardly add that I do not consider that such a fact of origin, could it be proved, would constitute any valid reason for raising the two Ape-groups into two distinct orders. Those, however, who take this view as to their origin, and who, at the same time, would make the Lemuroids an order on genetic grounds, should be logically compelled to take the same step with regard to the Simiadee and Cebidae. It will be asked, But can it be possible that two genera which possess so many points in common as Cebus and Cercopithecus have come to resemble each other independently ? I confess I cannot see any reason why they should not have so come. W e have abundant examples of separate points of resemblance which have independently arisen. Amongst such maybe mentioned the flying Squirrels and the flying Phalangers; the canines and premolars of Canis and Thylacinus, the grinders of Perameles and Urotrichus, and, as before mentioned, the cervical vertebrae of Auchenia and Myrmecophaga. As to the extremities, Didelphys and Phalangista, and, according to many, the Lemuroids also, show how an opposable inner digit may exist independently of inheritance. But if some naturalists are disposed to admit that the common origin of the Cebidce and Simiadee may be very doubtful, can they be even sure that Cercopithecus and Hylobates can claim a common Ape-ancestor ? In proposing these questions I am far from venturing to positively affirm the genetic distinctness of different Apes ; m y object is to obtain a decision as to the third question-namely, what is the more prudent course to follow as to the classification of such forms as may seem to be probably or possibly distinct in their origin ? I would urge that the more prudent course is to give to genetic considerations a decidedly subordinate place in questions of classification- and this on two grounds. If any two groups of animals can easily be joined together in a larger aggregation capable of distinct definition by numerous characters, easily discernible and drawn from structures important in the economy of life, then I submit such groups should be so joined, provided they do not constitute a whole inconvenient and unmanageable from the number of its subdivisions. As to the Cebidce and Simiadee, then, I say, if they are really one in origin, it is not on that account they should be kept united in the same order; and, similarly, if the Anthropoidea and Lemuroidea |