THE CLASSIFICATION OF THE VERTEBRATA. 191 



kingdoms ! Considering the various opinions held as to these 

 intrinsically uuiiniDortant and not very numerous groups of 

 animals, it seems more judicial in men of science to continue the 

 Classification of Vertebrata, as proposed by Professor Cleland, 

 into Fishes, Reptiles in the extended sense, Birds, and Mammals. 



The doctrine of Dohrn on Degeneration may have yet much to 

 say on the question of the origin of great divisions of animals, 

 and may seriously weaken the theory of evolution, as usually 

 understood, at certain of its points, as in this borderland between 

 the Vertebrate and Invertebrate sub-Kingdoms. To take two 

 higher steps in the supposed ladder of the Ascent of Man, the 

 Monotremata maj^ be no more than degenerate Marsupialia, and 

 not links in the chain between Reptiles and Marsupialia. The dis- 

 tribution of the Monotremata and Marsupialia in tlie Australian 

 Province would harmonize with this, and the fact that the 

 Ornithorhynchus in early life has teeth and loses them when full 

 grown, and that the other type, the Echidna, has none, would 

 tend to place them among Marsupialia of a degraded type, and to 

 show that they have developed by " progressive simplification 

 from their more elaborate ancestors." Again, the small mammals 

 known as Insectivora, which are looked upon as links between 

 certain Placental Mammals and Lemurs, may Treasonably be 

 considered to be degenerate Rodents, h-iving become degenerate 

 through their nocturnal subterranean and hybernating habits. 



Indeed, when the doctrine of Degeneration is given full play, 

 and the question of varieties fully borne in mind, a considerable 

 weakening of the theory of organic evolution as usually under- 

 stood may be anticipated. Tlie determinate evolution of Professor 

 Cleland is a much more philosophic conception than that in 

 which Natui'al Selection, with its indispensable partner, accidental 

 variation, is the main factor. Determinate evolution at any rate 

 harmonizes with the undeniable teleology which stares the 

 observer in the face, let the " naturalist " say what he will as to 

 secondary or natural causes. Here, whether one accepts the view 

 or not, supernatui-al causation of the life-history of the plants and 

 animals which people the earth finds expression. 



