160 PROBLEMS OF GENETICS 



of several shades of orange. The passerinii males from Nica- 

 ragua are indistinguishable from those of Colombia, and the 

 icteronotus of Ecuador are the same as those in Panama. The 

 orange intergrades, doubtless heterozygous forms, though col- 

 lected at the same locality (Medellin in Colombia) as several 

 pure yellows and pure scarlets, are in the British Museum series 

 sorted out as a separate species under the name chrysonotus! 

 Complications are introduced by the relations of these forms to 

 another named type, fiammigerus, but we may for our purpose 

 leave that out of consideration, and say that the order of geo- 

 graphical sequence from Honduras to Ecuador is (i) scarlet, 

 (2) yellow, (3) mixture of types, scarlet, yellow, orange, (4) 

 yellow. 



Similar examples exist in the birds of the old world, but I do 

 not know of any that have been studied so fully as those of 

 America. The best known is that of the two Rollers, Coracias 

 indicus which spreads from Asia Minor through Persia, Balu- 

 chistan, the Indian Peninsula and Ceylon, and affinis which 

 ranges from Nepal, through Assam, Tenasserim and the Indo- 

 Chinese countries. The two types are very different and may be 

 distinguished as follows: 



C. indicus C. affinis 



Mantle drab brown-chestnut. Dark olive-green. 



Breast chestnut. Dull purple brown. 



Throat purplish, streaked with white. Purple, streaked with blue. 



Upper tail-coverts indigo. Turquoise. 



The wings are the same in both. In the provinces of Nepal, 

 Sikhim, and Darjiling the two species coexist, with the result 

 that intergrades have been frequently recorded. The line of 

 intergradation extends to the coast, and birds showing various 

 combinations of the two types from the Calcutta district exist 

 in collections. 12 The case is interesting inasmuch as like that of 

 Quiscalus it shows a series of combinations of various metallic 

 colours. Some of these are probably evoked by the development 

 of pigment behind striations or other interferences already exist- 

 ing, but in the present state of knowledge it would be quite im- 



w References on this subject will be found in Brit. Mus. Cat. Birds, XVII, p. 13. 



