CHAPTER V 



REVERSION AND ALLIED PHENOMENA 



" A man can never deny his ancestry." — Laws of Manu. 



" Evolution ever climbing after some ideal good. 



And Reversion ever dragging Evolution in the mud." — Tennyson. 



§ I. What is meant by Reversion. 



§ 2. Suggested Definitions. 



§ 3. Theoretical Implications. 



§ 4. Phenomena sometimes confused with Reversion. 



§ 5. " Skipping a Generation." 



§ 6. Splitting of Hybrids. 



§ 7. Reversion in Crosses. 



§ 8. Reversion of Retrogressive Varieties. 



§ 9. Interpretations in Terms of Reversion. 



§ 10. Further Examples of Reversion. 



§ I. What is meant by Reversion 



Most evolutionists — indeed, most naturalists — have ranked 

 reversion as one of the facts of inheritance. Thus Darwin 

 said (1881) : " Any character of an ancient, generalised, or 

 intermediate form may, and often does, reappear in its descend- 

 ants after countless generations." Wallace, Spencer, Galton, 

 and Weismann have all used the concept " reversion " as a 

 convenient way of summing up a universally admitted series of 

 cases, where organisms exhibit ancestral traits which their 

 parents did not possess. As a descriptive term for summing up 

 these cases, the word " reversion " is useful, convenient and, it 



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