The doctrine of descent and Darwinism . a,) wepossess mammals which are manifestly far beneaththe Marsupials, we are referred entirely to conjectureand inference for the origin of the mammals. Thesepoint to amphibian-like beings, in \vhich certain pe-culiarities of the mammalian skull, such as the doublecondyle of the occiput, were prefigured, and whichby the formation of the amnios and allantois ap-proached the true reptiles. These progenitors of theMammalia are not, however, represented in any orderof reptiles or amphibians now extant. The pedigree(p. 269) in which we have grouped the more a
The doctrine of descent and Darwinism . a,) wepossess mammals which are manifestly far beneaththe Marsupials, we are referred entirely to conjectureand inference for the origin of the mammals. Thesepoint to amphibian-like beings, in \vhich certain pe-culiarities of the mammalian skull, such as the doublecondyle of the occiput, were prefigured, and whichby the formation of the amnios and allantois ap-proached the true reptiles. These progenitors of theMammalia are not, however, represented in any orderof reptiles or amphibians now extant. The pedigree(p. 269) in which we have grouped the more accuratelyknown fossil Mammalia with those now living, containsconsiderable gaps, and rests in a great measure onhypothesis, but it gives, nevertheless, with approximateprobability a correct representation of the consanguinityof the orders, and in comparison with the system as itwas constructed in the school-books prior to the revivalof the doctrine of Descent, it must be esteemed a greatand suggesti\/e advance. PEDIGREE OF MAMMALS. 26q. 2/0 THE DOCTRINE OF DESCENT As regards the structure of their skull, the constitutionof the pectoral arch, and their persistence in the phase(embryonic in other mammals) in which the rectumand the urinary and genital ducts open into a singlecloaca, the Monotremata (Ornithorhynchus, Echidna),limited to Australia and Tasmania, are the lowest mem-bers of their class, and must be considered as remnantsof a division reaching from indeterminable past agesdown to the present time. It may be presumed thatthe Marsupials were developed from an analogous powers of adaptation have been chiefly testifiedin Australia, where the subdivisions of the order, usuallydesignated as families, are, in dentition and habits of life,developed in a manner analogous to several of thoseorders which appear on the second great scene of mam-malian development, namely, the Northern hemisphere. Far advanced beyond the Monotremata as to skeleton,they remain on a low g
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Keywords: ., bookauthorschmidtd, bookcentury1800, bookdecade1880, bookyear1882
