Chap. XIII. 



REVERSION. 



39 



former generation ; but in the following cases the characters 

 which thus reappear formerly appertained to the species, and 

 were lost at a more or less remote epoch. Thus, according 

 to Azara, 24 the calves of a hornless race of cattle which originated 

 in Comentes, 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. 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." 25 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. 26 Now, as G-allus banhiva is coloured red and orange, 

 and as Dorking fowls and both kinds of 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 Reversion. — 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 reappearance 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 cannot 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 pre- 



24 'Essais Hist. Nat. du Paraguay,' 

 torn, ii., 1801, p. 372. 



25 These facts are given on the high 

 authority of Mr. Hewitt, in 'The 



Poultry Book,' by Mr. Tegetmeier, 1866, 

 p. 248! 



26 < The Poultry Book,' by Tegetmeier, 

 1866, p. 97. 



