44 Mr. T. H. Huxley on the Method of Palceontology» 



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 physiological correlation be- 

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

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

 order to the due performance of a given function in any case it is 

 impossible that the organs performing that function should be 

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

 Thus the teeth 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 we have 

 no reason for affirming this to be a necessary })hysiological corre- 

 lation, in the sense that no other could equally fit 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 m.ore uniform than the 

 physiological ends w^hich have to be attained by living beings ; 

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

 and it would, I think, in the face of these well-known facts, be 

 the height of presumption to affirm that the function which we 

 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, we have no right to say with Cuvier, 

 that " Every organized beuig 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 physiological 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. Oii^ 

 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 Cuvier^s law of correlation, and, ambiguously^ 

 supported by Cuvier's phraseology elsewhere, have imagined the 

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

 iogical research. 



