THE CLASSIFICATION OF THE VERTEBEATA. 187 



and ]imb are at their maximum of development in Fishes while 

 the brain is at its minimnni. In Birds, which have remark- 

 able thoracic development in connection with circulation 

 and respiration, the pectoral limb has the hand abortive, and 

 in Mammals, which are specially remarkable for the advance 

 in size and structure of the brain, the cpiadrate bone which 

 hitherto supported the lower jaw is reduced to an ossicle of 

 the ear, and the jaw itself is simpler than in any other 

 vertebrates. 



The Chairman (D. Howard, Esq., D.L.). — We have to thank 

 Dr. Cleland for bringing- before ns a papei' of verj' great interest, 

 and Mr. Slater for so kindly reading it. 



The whole question of Comparative Anatomy, as we used to call 

 it and to which the word evolution may be very fairly applied, 

 especially in the sense used by Dr. Cleland, is one of the most 

 fascinating studies that it is possible to pursue. 



It requires an expert to speak on such a difficult subject. But to 

 any of us who have not the privilege of being experts it is simply 

 one of those fields of study which always afford great interest. 

 I would venture to call attention to the very clear and decided 

 way in which the author of the paper defines two things which 

 are so often seriously confused. 



The idea of Evolution cannot, I think, be studied without seeing 

 that it is absolutely essential clearly to distinguish between a 

 process of evolution and the cause of that evolution ; to many 

 people's minds, the idea of evolution is solely confined to evolution 

 by Natural Selection. Here we have the writer of the paper, who 

 has certainly grasped the relations of different organisms as few 

 have, and yet has no doubt, in his own mind, about the conceivable 

 possibility of mere accident or environment having been the 

 governing factor in that remarkable chain of events. 



J. Hutchison, Esq., M.D., F.R.S.- — -I see a statement in the paper 

 that there is no similarity between the skulls of birds and of 

 reptiles. Is it not forgotten that there is a remarkable similarity 

 in the case of the single occipital condyle ? 



Inspector- General J. D. Macdoxald, F.R.S. — I have spent mora 



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