“In the marsupials the chromosome number is a low one and in the opossum is 22. At first sight it might appear that the eutherian condition might have arisen from this by tetraploidy. There are two objections, however. In the first place the bulk of the chromatin in marsupials is about the same as in the eutheria, using the sex chromosome as our measure. In the second place, polyploidy could scarcely occur successfully in animals with X-Y sex chromosomes, as most mammals possess, because of the complication occurring in the sex chromosome balance” (_Science_, April 17, 1925, p. 424). As the X-Y type of sex chromosomes occurs widely not only among vertebrates, but also among insects, nematodes, and echinoderms, Painter’s latter objection excludes evolution by polyploidy from a large portion of the animal kingdom. NOTE TO PAGE 90.— Especially reprehensible, in this respect, are the reconstructions of the Pithecanthropus, the Eoanthropus, and other alleged pitheco-human links modeled by McGregor and others. These imaginative productions, in which cranial fragments are arbitrarily completed and fancifully overlayed with a veneering of human features, have no scientific value or justification. It is consoling, therefore, to note that the great French palæontologist, Marcelin Boule, in his recent book “Les Hommes Fossiles” (Paris, 1921), has entered a timely protest against the appearance of such reconstructions in serious scientific works. “Dubois and Manouvrier,” he says, “have given reconstructions of the skull and even of the head (of the Pithecanthropus). These attempts made by medical men, are much too hypothetical, because we do not possess a single element for the reconstruction of the basis of the brain case, or of the jawbones. We are surprised to see that a great palæontologist, Osborn, publishes efforts of this kind. Dubois proceeded still farther in the realm of imagination when he exhibited at the universal exposition of Paris a plastic and painted reproduction of the Pithecanthropus” (_op. cit._, p. 105). And elsewhere he remarks: “Some true savants have published portraits, covered with flesh and hair, not only of the Neandertal Man, whose skeleton is known well enough today, but also of the Man of Piltdown, whose remnants are so fragmentary; of the Man of Heidelberg, of whom we have only the lower jawbone; of the Pithecanthropus, of whom there exists only a piece of the cranium and ... two teeth. Such reproductions may have their place in works of the lowest popularization. But they very much deface the books, though otherwise valuable, into which they are introduced.” ... “Men of science—and of conscience—know the difficulties of such attempts too well to regard them as anything more than a pastime” (_op. cit._, p. 227). NOTE TO PAGE 342.—