_Propliopithecus_, or _Dryopithecus_? Hylobatic, or troglodytic affinities? Such questions are scarcely the pivots on which the world is turned! Nevertheless, we rejoice that Doctor Gregory has again settled the former problem (provisorily, at least) to his own satisfaction. More important, however, than that of the dentition of _Dryopithecus_, is the crucial question of whether or not Palæontology is able to furnish evidence of man’s genetic continuity with this primitive pithecoid root. Certainly, no effort has been spared to procure the much desired proofs of our reputed bestial ancestry. The Tertiary deposits of Europe, Asia, Africa, America, and the oceanic islands have been diligently ransacked for fossil facts that would be susceptible to an evolutionary interpretation. The aprioristic criterion that all large-brained men are recent, and all small-brained men with recessive chins are necessarily ancient, has always been employed in evaluating the fossil evidence. Notwithstanding all endeavors, however, to bring about the consummation so devoutly desired, the facts discovered not only fail to support the theory of collateral descent, but actually militate against it. For assuming that man and the anthropoid apes constitute two distinct lines of evolution branching out from common Tertiary or pre-Tertiary stock, palæontology should be able to show numerous intermediate fossil forms, not alone for the lateral branch of the apes, but also, and especially, for the lateral line connecting modern men with the common root of the primate tree. But it is precisely in this latter respect that the fossil evidence for collateral descent fails most egregiously. Palæontology knows of many fossil genera and species of apes and lemurs, that might conceivably represent links in a genetic chain connecting modern monkeys with Tertiary stock, but it has yet to discover so much as a single fossil species, much less a fossil genus, intermediate between man, as we know him, and this alleged Tertiary ancestor common to apes and men. Not even catastrophism can be invoked to save this irremediable situation; for any catastrophe that would have swept away the human links would likewise have swept away the ape links. The presence of many genera and species of fossil apes, in contrast to the absence of any fossil genus or species of man distinct from _Homo sapiens_, is irreconcilable with the theory of collateral descent. Such is the dilemma proposed to the upholders of this theory by Wasmann, in the 10th chapter of his “Die Moderne Biologie” (3rd edition, 1906), a dilemma, from which, as we shall see, their every attempt to extricate themselves has failed most signally.