248 The Progress of Zoology . 



refused to take positions among vertebrates, or insects. To 

 form a fair estimate of the progress of zoology in the classifica- 

 tion of the Orders in the vast stretch between Batrachians and 

 Zoophytes, the Sy sterna Naturce must be explored, and its 

 method of dealing with these compared with the labours of 

 Cuvier and his successors. Still the principles of classification 

 have remained nearly the same, at least since Cuvier, proving 

 how truly he seized upon the characteristics really indicative of 

 structural and physiological relationships. The most important 

 proposal for a redistribution is that of Professor Owen for the 

 division of the Mammalia into two great groups, the designations 

 of which are self-explanatory. Under Placentalia he ranges all 

 the higher mammalian forms in the same order as in Cuvier' s 

 scheme, but the marsupiates and monotremes are separated to 

 form another grand division called A-placentalia, in which the 

 monotremes are ranged to correspond to the edentates in the 

 first division, and as their counterparts with a less perfect mode 

 of reproduction. But this, though based on obvious and 

 important distinctions, appears to have found little favour with 

 zoologists, and, like the labours of Grant and Blainville on the 

 nervous system, is valued more for the prominence it gives to 

 certain physiological facts than for its adaptability to the pur- 

 poses of classification in the present transition state of zoological 

 science. These things are, however, the proper fruit of the 

 labours in philosophical zoology which have been conducted 

 with such ardour in Europe during the past half century, and 

 we seem now to be waiting for a second Cuvier who shall boldly 

 grasp the distinctive features of the animal kingdom, and 

 arrest for a time the growing tendency to trifle with zoological 

 landmarks by a revision of all boundary lines, and fitting into 

 their proper places all that is true and durable in the various 

 systems that have been of late propounded. 



The frequent varying of the basis of classification, though 

 inevitable, is not the less destructive to harmony, and that 

 correspondence of mutual relationships which a system professes 

 to unfold. That homologies of structure are to be regarded as 

 of the first importance in the determination of the place an 

 animal is to occupy in a natural system is self-evident ; but it is 

 worth asking, whether a purely artificial system would not serve 

 as useful a purpose in zoology as it has done in botany, because 

 it could be framed once for all, and serve for comparison at any 

 future time with a progressive natural system, which of neces- 

 sity can never be perfect. Pliny excites the laughter of the 

 young naturalist when he describes the cat as the only bird 

 that suckles its young; but a strictly homomorphic system 

 would have its value, and the wonder is that no one has 

 ventured hitherto to propose a scheme of the kind. Bats, 



