150 GENETICS 



babies and some adults which resemble the ridges 

 in the roof of a cat's mouth ; the vermiform appen- 

 dix, a necessary part of the digestive apparatus of 

 many animals but fraught so often with evil conse- 

 quences to man ; these and scores of similar charac- 

 ters, which, taken together, make man in the eyes 

 of the comparative anatomist a veritable old curi- 

 osity shop of ancestral relics, are the last traces of 

 characters which formerly had a significance in some 

 of man's forbears. Having lost their usefulness, 

 these structures still hang on to the anatomical 

 household as pensioners. They have not been re- 

 called from the past, but have always been with us, 

 although of diminishing importance. In no sense, 

 therefore, can they be called reversions. 



* . c. Acquired Characters resembling Ancestral Ones 



Sometimes the drunken descendant of a drunken 

 great-grandparent has acquired this characteristic 

 through his own initiative quite aside from any an- 

 cestral contribution to his germplasm. This is not 

 reversion. It is a reacquisition which resembles 

 the ancestral condition. 



Again, tame animals that run wild acquire habits 

 resembling those of their wild ancestors, but this is 

 not necessarily reversion. It is the natural response 

 of feral animals to the conditions of wild life. 



d. Convergent Variation 



The European hedgehog, Erinaceus, an insecti- 

 vore, the American porcupine, Erithizon, a rodent, 

 and the Australian spiny anteater, Echidna, a 



