The Origin of Whales and Carnivores 195 



later steps of the transformation, by which the mastodons lost their 

 lower tusks, and their relatively small and simple grinding teeth 

 acquired the great size and highly complex structure of the true 

 elephants, may be followed in the uppermost Miocene and Pliocene 

 fossils of India and southern Europe. 



Egypt has also of late furnished some very welcome material 

 which contributes to the solution of another unsolved problem which 

 had quite eluded research, the origin of the whales. The toothed- 

 whales may be traced back in several more or less parallel lines as 

 far as the lower Miocene, but their predecessors in the Oligocene are 

 still so incompletely known that safe conclusions can hardly be drawn 

 from them. In the middle Eocene of Egypt, however, has been 

 found a small, whale-like animal (Protocetus), which shows what 

 the ancestral toothed-whale was like, and at the same time seems 

 to connect these thoroughly marine mammals with land-animals. 

 Though already entirely adapted to an aquatic mode of life, the 

 teeth, skull and backbone of Protocetus display so many differences 

 from those of the later whales and so many approximations to those 

 of primitive, carnivorous land-mammals, as, in a large degree, to 

 bridge over the gap between the two groups. Thus one of the most 

 puzzling of palaeontological questions is in a fair way to receive a 

 satisfactory answer. The origin of the whalebone-whales and their 

 relations to the toothed- whales cannot yet be determined, since the 

 necessary fossils have not been discovered. 



Among the carnivorous mammals, phylogenetic series are not so 

 clear and distinct as among the hoofed animals, chiefly because the 

 carnivores are individually much less abundant, and well-preserved 

 skeletons are among the prizes of the collector. Nevertheless, much 

 has already been learned concerning the mutual relations of the 

 carnivorous families, and several phylogenetic series, notably that of 

 the dogs, are quite complete. It has been made extremely probable 

 that the primitive dogs of the Eocene represent the central stock, 

 from which nearly or quite all the other families branched oif, though 

 the origin and descent of the cats have not yet been determined. 



It should be clearly understood that the foregoing account of 

 mammalian descent is merely a selection of a few representative 

 cases and might be almost indefinitely extended. Nothing has been 

 said, for example, of the wonderful museum of ancient mammalian 

 life which is entombed in the rocks of South America, especially of 

 Patagonia, and which opens a world so entirely different from that of 

 the northern continents, yet exemplifying the same laws of " descent 

 with modification." Very beautiful phylogenetic series have already 

 been established among these most interesting and marvellously 

 preserved fossils, but lack of space forbids a consideration of them. 



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