INHERITANCE OF SMALL VARIATIONS 241 



cessively rare compared with the numerous finely gradated 

 forms that may be found connecting a mimetic form 

 with a non-mimetic or transitional between two mimetic 

 forms. 



That birds do exercise discrimination and do destroy 

 large numbers of butterflies there can no longer be doubt, 

 thanks to Swynnerton. It seems difficult to avoid the 

 conclusion that the conspicuous mimics are ^preserved 

 by selection, and it is on the question how they arose 

 that Darwinians and mutationists join issue. 



The study of a mimic of wide distribution and changing 

 form, such as Acraea alciope, Pseudacraea eurytus, Charaxes 

 etheocles, shows by the transition stages that a mimic 

 is not suddenly turned out complete. Evidence may be 

 found in the publications of the Entomological Society ^ 

 that the small, often quite small, variations on which 

 a Darwinian depends, are heritable, whereas, according 

 to the mutationist, such " fluctuations " are not handed 

 down. On the other hand, the mutationist claims that 

 his large variations are irrevocably fixed, and, when once 

 formed, do not retrogress towards the parent form. Thus, 

 for instance, the wonderful forms of Pseudacraea eurytus, 

 mimicking different species of Planema according to the 

 locality, should, if the model ceased to exert its influence, 

 still continue to show the same great degree of resemblance 

 without the occurrence of any intermediate variations. 

 The next chapter, however, shows that this is not the 

 case. 



^ Poulton, E. B., "Heredity in Six Families of P. dardanus, subsp. 

 ceneay Trans. Ent. Soc, 1908r Carpenter, G. D. Hale, " The Inherit- 

 ance of Small Variations in the Pattern of Papilio dardanus." Trans. 

 Ent. Soc, 1914. 



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