ON VARIATION. 37 



spots have disappeared altogether, so that the body is 

 more or less completely encircled by pairs of black 

 rings, the alternating spots having disappeared. This 

 might be supposed to have resulted from a continua- 

 tion of the process by which the alternating spots have 

 disappeared, and the edges of the saddles been brought 

 closer and closer together. The continued transverse 

 extension of the spot color would finally obliterate the 

 lateral borders completely, as actually occurs in this 

 last form, the coccinea of authors, which is the com- 

 mon type of the Gulf Coast. But the black has not 

 covered the head and muzzle of this form as in the an- 

 nulata. These- regions are on the contrary red, as is 

 the spot color generally, while the ground color is pale 

 yellow. 



A tendency to a development of black pigment in 

 the saddle spots is seen in two other forms. The sub- 

 species gentilis resembles annulata, but has a black 

 longitudinal dorsal band which divides each saddle 

 spot in two equal halves. This is a rare form, only 

 known from the Indian Territory. The common Mex- 

 ican form {polyzona} has the paired rings of coccinea, 

 the black head of annulata, but each scale of the red 

 intervals is tipped with black. 



The relations of these forms may be expressed in a 

 tabular form, given on page 39. 



The main series corresponds with a distribution in 

 latitude, commencing with the triangula of New Eng- 

 land and New York, and passing gradually to the coc- 

 cinea of the Gulf Coast regions, and polyzona of Mex- 

 ico and Central America. The forms of the right-hand 

 column are (except the parallela) from the central 

 warmer parts of the continent. 



This series of color- forms of the Osceola doliata 



