4A Mr. T. 11. Huxley on the Method of PaI<tontology. 



suppose that it ever has entered, or ever will enter, into the 

 mind of any person conversant with the rudiments of that sci- 

 ence to question the existence of physioloi^ieal correlation be- 

 tween the different parts of animals. Hut how far that corre- 

 lation is in any case to be called nrcessnri/ ; that is, how far in 

 order to the due |)erforiiiancc of a given function in any case it is 

 impossible thiit the organs performing that function should be 

 different from what we find them to be, is quite another question. 

 Thus the teetii of a lion and the stomach of the animal are in 

 such relation that the one is fitted to digest the food which the 

 others can tear ; they are physiologically correlated, but wc have 

 no reason for afhrming this to be a necessary |)iiysiological corre- 

 lation, in the sense that no other could equally tit its possessor 

 for living on recent flesh. The number and form of the teeth 

 might have been quite different from that which we know it to 

 be, and the construction of the stomach might have been greatly 

 altered, and yet the function of these organs might have been 

 equally well performed. Nothing can be more uniform than th(! 

 physiological ends which have to be attained by living beings ; 

 nothing more various than the modes in which they are attained ; 

 and it w(»uld, I think, in the face of these well-known facts, be 

 the height of j)resumption to affirm that the function which wc 

 see in any case performed in a particular way could not possibly 

 have been performed in any other mode. 



If physiological correlations are however not necessary ; if, so far 

 as physiology is concerned, wc have no right to say with Cuvier, 

 that " Every organized being constitutes a whole, a single, and 

 complete system, whose parts mutually correspond and concur by 

 their reciprocal reaction to the same definite end. None of these 

 parts can be changed without affecting the others, and conse- 

 quently each taken separately indicates and gives all the rest;'* — 

 then a very important consequence follows, viz. that it is quite 

 impossible to reason conclusively on j)hysiological grounds alone 

 from any part of a living being to the whole. 



I by no means assert that Cuvier, in enunciating the propo- 

 sition quoted above, meant to exclude all but physiological con- 

 siderations so completely as the words appear to indicate. On 

 the contrary, his practice, no less than other passages of the re- 

 markable essay from which that citation is taken, shows clearly 

 that no man more fully understood the value of morphology. 

 Nevertheless the words of the proposition are distinct enough to 

 justify those who, guided more by authority than by right reason, 

 have denominated it Cuvicr's law of correlation, and, ambiguously 

 supported by Cuvicr's phraseology elsewhere, have imagined the 

 principle which it involves to have been his guide in palaeonto- 

 logical research. 



