52 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



Ichthyosaurs with the group of Fishes, under the 

 rather superficial pretext of polydactylism. Finally, 

 the existence of a double occipital condyle in the 

 Amphibians and Mammals, as opposed to the single 

 condyle of the Reptiles, appears now to have lost 

 much of the importance formerly attributed to it 

 as a proof of the direct amphibian origin of the 

 Mammals. 



But let us return with Haeckel to this last group, 

 the most interesting of all, since it contains the 

 beings highest in organization and, in particular, 

 Man. Our author considers the Mammals as having 

 issued from a group of animals of the Triassic epoch 

 which must have possessed many of the charac- 

 teristics of the actual Monotremata, including the 

 Echidna and the Ornithorhyncus of New Holland. 

 These essential characteristics must have been : 

 the presence of a cloaca, at once the vestibule of 

 the digestive and genito-urinary passages, the weld- 

 ing of the two clavicles into a forked bone and the 

 existence of a well developed coracoid, all equally 

 very early characteristics. But these primitive 

 hypothetical Monotremata must have possessed 

 toothed jaws instead of the horny beak of the only 

 two existing descendants in Australia of this group. 



The Marsupials or Pouched Mammals would con- 

 stitute a link between the Monotremes and the 

 higher Mammals or Placentals. This group of 

 Marsupials, still richly represented in Australia and 

 in America, is however in course of vanishing and 

 must have been at its apogee towards the middle 

 of Secondary times. In any case, it is certain that 

 all the known remains of mammals of the Secondary 



