184 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



characters. Here is one case where we see that characters can not be said to pre- 

 exist as definite units, the same bird may pass through several stages of patterns 

 in succession, and we always .sec the transitions from one character to another. 

 Similar examples could be drawn from the geopelias and other doves. 



In 1905 I raised a whitened female pheasant which in her second year became 

 nearly normal in color, but somewhat paler. From her and a normal male I obtained 

 a partial albino male; but, strange to say, this two-thirds white male subsequently 

 assumed gradually the color of the normal male, and finally when 2 years old had 

 lost all white and presented the plumage of a normal male, except that the colors 

 were not quite so dark." 



Albinism is, then, not one of a pair of opposite or alternative characters; it is 

 only one of many degrees of the same color-character. Black pales to gray, and 

 gray to various degrees of whiteness. In the pigeon the fancier's black, brown- 

 gray, gray, red, yellow, all stand for one and the same kind of melanin pigment, 15 

 differing only in density, depth, etc. The lighter colors and shades graduate into 

 white, which, when closely examined, usually shows a tinge of yellowish or orange 

 brown. If the pigment granules be examined by transmitted light we get an orange 

 brown; if by reflected light, then black, red, yellow, whitish. Breeding shows that 

 we pass easily from one of these conditions to another. The variations are all 

 quantitative and conditional states of one and the same thing. Mendelian pro- 

 portions may or may not appear, but these proportions are not to be construed as 

 unit-characters, nor yet as immutable characters. I am convinced that these 

 various shades of color are all due to one and the same character; in the develop- 

 ment they are severally presented under different conditions. 



In many animals we have a summer color and a winter white. Both are the 

 same character, but in extreme conditions. The degree of exhibition may depend 

 on the degree of heat, light, etc. How much simpleT is this view than the assump- 

 tion of two unit-characters, alternating in the same animal from summer to winter 

 and back. 



Physical weakness. A Juvenal pigeon (OS-D 3-G) hybrid from a male orientalis 

 turtur-risoria-alba (OS 8-D 3} and a female blond ring, hatched July 18, 1908, has 

 only 11 tail-feathers and 2 abnormal toes. The fourth toe of each foot has an 

 abrupt bend at the end of the basal third, the distal two-thirds taking a direction 

 nearly parallel with the middle or third toe. The result is "symmetrical" on the 

 two sides. The tail, toes, and rather small size all indicate that this bird owes 

 its deformities and deficiencies to weakness in development. (W 9) (The color of 

 this bird see table 57 too, was an abnormal gray, found in one other of its many 

 sisters and brothers. This gray-colored bird (OS-D 3-G) arose almost immediately 

 before a period of complete failure of developmental energy; the other abnormal 

 gray was from the first egg after this period that was able to develop at all. EDITOR.) 



Weakness in common pigeons is frequently expressed in white color. Some 

 white pigeons fail to get an orange-red iris. The irides of white ring-doves some- 

 times remain dark; the same is true in some common pigeons. 



11 The author lias recorded several instances of the appearance of white color due to quite temporary or acci- 

 dental causes. It seems hardly necessary to refer to such cases in this work, since similar cases are well known to all 

 naturalists. -EDITOR. 



ls The editor has presented (Biol. Bull., 1909) evidence from chemical and developmental standpoints for this 

 same conclusion, which was reached earlier by Professor Whitman. EDITOR. 



