Chap. XIII. REVERSION. 13 



generations ; but characters sometimes reappear in the same 

 manner after a much longer interval of time. Thus the 

 calves of a hornless race of cattle which originated in 

 Corrientes, though at first quite hornless, as they become 

 adult sometimes acquire small, crooked, and loose horns ; and 

 these in succeeding years occasionally become attached to the 

 skull. 25 White and black Bantams, both of which generally 

 breed true, sometimes assume as they grow old a saffron or 

 red plumage. For instance, a first-rate black bantam has 

 been described, which during three seasons was perfectly 

 black, but then annually became more and more red ; and it 

 deserves notice that this tendency to change, whenever it 

 occurs in a bantam, " is almost certain to prove hereditary." 26 

 The cuckoo or blue-mottled Dorking cock, when old, is liable 

 to acquire yellow or orange hackles in place of his proper 

 bluish-grey hackles. 27 Now as Gallus bankiva is coloured red 

 and orange, and as Dorking fowls and bantams are descended 

 from this species, we can hardly doubt that the change which 

 occasionally occurs in the plumage of these birds as their age 

 advances, results from a tendency in the individual to revert 

 to the primitive type. 



Crossing as a direct cause of Beversion. — It has long been 

 notorious that hybrids and mongrels often revert to both or 

 to one of their parent- forms, after an interval of from two to 

 seven or eight, or, according to some authorities, even a greater 

 number of generations. But that the act of crossing in itself 

 gives an impulse towards reversion, as shown by the reap- 

 pearance of long-lost characters, has never, I believe, been 

 hitherto proved. The proof lies in certain peculiarities, which 

 do not characterise the immediate parents, and therefore can- 

 not have been derived from them, frequently appearing in the 

 offspring of two breeds when crossed, which peculiarities 

 never appear, or appear with extreme rarity, in these same 

 breeds, as long as they are precluded from crossing. As this 



25 Azara, « Essais Hist. Nat. de 'The Poultry Book,' by Mr. Teget- 



Paraguay,' torn. ii. 1801, p. 372. meier, 1866, p. 248. 



28 These facts are given on the 27 ' The Poultry Book,' by Teget- 



high authority of Mr. Hewitt, in meier, 1866, p. 97. 



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