230 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



To sum up, the phenomena of convergence 

 noticed in nearly all the groups of fossil animals 

 seem to me to have been singularly exaggerated. 

 In the majority of cases the similarities of this 

 nature are very superficial, are easily explained by 

 the facts of adaptation to common functions, and 

 only affect a small number of organs, the limbs, 

 the dermic plates, the teeth, or the shell, according 

 to the group. Almost always it is easy for the 

 naturalist to unmask these deceptive analogies 

 by appealing to the organization as a whole. It 

 is only in a very small number of cases, in the order 

 of the Ammonites, in particular, that Nature, 

 powerless to vary indefinitely the processes of 

 ornamentation on a shell coiled on itself, has repro- 

 duced repeatedly in the series of ages, analogous or 

 almost identical forms, susceptible of momentarily 

 misleading the observer in his researches as to the 

 natural relations of the numerous genera of this 

 great order. 



