WAYS OF CONVERGENCE 53 



characters as have been developed by adapta- 

 tion, quite independently of the affinities of 

 animals, from such as have been transmitted by 

 inheritance through a long series of generations. 1 



Morphology therefore naturally falls into two 

 divisions : convergent morphogeny and homo- 

 genetic or normal morphogeny. The former is 

 not generally admitted as a legitimate branch 

 of positive morphology ; the latter is the way 

 usually followed, and common characters which 

 are not homologous are sometimes attributed 

 to "mere convergence." It appears that there 

 is more joy amongst morphologists over one 

 attempt at genealogy than over ninety and nine 

 demonstrations of convergence. Personally, I 

 take the view that both of the above-named 

 divisions of morphology are equally important. 



There are several ways of convergence and 

 each is expressed in various degrees of intensity. 

 The two most widely diffused ways of con- 

 vergence are known respectively as homoplasy 2 

 and mimicry. 



True mimicry is defined by Mr Alfred Russel 

 Wallace 3 as "a form of protective resemblance 

 in which one species so closely resembles 

 another in external form and colouring - as to 



1 Karl Semper, "The Natural Conditions of Existence as they 

 affect Animal Life." Fourth edition, London, 1890. 



2 The term and idea of homoplasy were introduced by Sir E. 

 Ray Lankester : " On the Use of the Term Homology in Modern 

 Zoology," Ann. Nat. Hist., 1870. 



3 A. R. Wallace, " Darwinism." Second edition, London, 1890. 



D 2 



