178 



PROF. JOHN CLELAND, M.D.^ ETC., ON 



crocodiles. This change becomes all the mo]-e accentuated 

 when Ave consider that Owen looked on Ciivier's two lower 

 gronps as deserving to be united in one great division ot 

 H^matocrya or cold-blooded animals, contrasting with the 

 warm-blooded Birds and Mammals ; while Huxley joined 

 together the Fishes and Amphibians under the name ui 

 Ichthyopsida and in like manner joined the restricted Reptiles 

 with the Birds under the name of the Sauvopsida, while he 

 kept the Mammals completely separate. 



It will be perceived that the Reptilia of Cuvier is the 

 gi-oup which has specially been the subject of different 

 opinions. One authority, recognising it as justly to be 

 regarded as a coherent whole, considered it as separated 

 widely from Birds, while another agreeing with hjm, as every 

 one will do, on the question of the nearness of Fishes to 

 Amphibians, looked on the whole remainder of Cuvier s 

 Reptiha as far removed from them and having a near 

 affinity to Birds. 



To consider such a dispute rightly it must be remembered 

 that classification has in recent times had quite a different 

 function and importance from what it once had. The first 

 attempts at classification are liable to be of a highly artificial 

 kind like the Linnean system in Botany, principally useful 

 in enabling large numbers of species to be easily distinguished. 

 But inevitably a natural arrangement makes itself known 

 where there is an abundance of species with great numbers of 

 important characters in common. More and more mere resem- 

 blance of analogy is distinguished from integral unity of struc- 

 ture, and the idea of affinity becomes clearly defined. This is 

 the stage which in Zoology became thoroughly established 

 under the auspices of Cuvier, but up to a much later date the 

 majority of zoologists and even anatomists gave little regard 

 to other than adult forms. In Cuvier's day the knowledge 

 of the real constitution of organs was comparatively limited 

 owing to the circumstance that Embryology was in its infancy, 

 and generally supposed, on account of the great difficulties 

 Avhich beset it, to be a study unlikely to throw much light on 

 questions of relationship of different animals. It is in this 

 way that one must largely account for what is, perhaps, the 

 greatest error that Cuvier fell into, the formation of the great 

 division Radiata, objected to even by his devoted admirer 

 Owen, in language quoted from Rudolphi, as '' a chaotic 

 group." 



Once the idea of development gets its legitimate place 



