114 IMIKKITAXCK. KKKTII.ITY. AND SEX IX PIGEONS. 



There are certainly very clear differences between them. For example, in the young 

 bird of the darker species there is a rich supply of "down," the bird being well covered with 

 it. This down has a characteristic appearance, being here rather coarser and shorter than 

 in the domestic pigeon. In the young of the white bird there is scarcely any down; at first 

 sight they seem almost perfect!}' naked, and are in this respect very distinct from blond 

 rings and from all other related species. The eggs of the white variety are on the average a 

 little smaller, and the species itself is a little smaller than the blond ring. The white variety 

 weighs a little less, and is a little more delicate in all its characters. It is certainly not as 

 strong a species as the dark or blond ring, but the general behavior of the two forms agrees 

 very closely; there is a mark on the neck of the white bird which also reveals a close affinity. 

 At first sight the white bird seems to lack the very prominent black collar of the blond 

 birds, but on closer examination the feathers of the region of the collar are found to have a 

 slightly yellowish tinge. There is no doubt about its having the mark or imprint of the 

 "ring" or collar. 



I began my experiments in crossing by making the reciprocal crosses. In one case a 

 white male was mated with a brown female; in the other, a brown male was used with a 

 white female. From this last cross I obtained during the first summer some 15 birds, all 

 of which were of the dark color. There was, however, a difference in depth of color among 

 these offspring. Some were light brown, while others were dark, darker even than the dark 

 parent. In the first cross, where a white male with a brown female were used, something 

 less than half the birds were white; the rest of them were light isabelline. 



The results of the second year's work with these first-generation hybrids were as follows: 

 Three pairs were mated. The males were all of the light color (one shown in pi. 25), 

 all having been derived from a pair in which the male was white and the female brown 

 (c? alba x 9 risoria). The females were from the other family, where the father was brown 

 ( 9 risoria x 9 alba), and most of these females were of the darker color. One pair I gave to 

 Dr. Watase, who kept an account of the results. He obtained 10 young during the summer. 

 In one case, I believe, an egg was broken before the young hatched, and he was unable to 

 tell what the color would be. Of the others which he succeeded in raising, 5 were white 

 and 5 of the darker color. 



From my own summer's work with 3 pairs of parents I have only 1 dark and 1 white 

 bird alive; 2 have died. I have found these species very convenient ones for experimenta- 

 tion, but during the present summer these birds have been used chiefly for taking care of 

 the young of other birds; this has prevented my getting more of their own young from them. 

 The point of chief interest in these results is this: In all these pairs, every one of the parents 

 being brown, we get quite a large proportion of white young birds. In other words, the white 

 color of the parent bird shows not in the second, but in the third generation.* (A 1/1) 



The results 5 of the alba x risoria cross are given in table 127. There were 5 

 young which resembled risoria and are called "light brown"; 4 young are designated 

 "white." The few white birds whose sex was known w r ere females; the 3 "light 

 brown" birds of known sex were males. The reciprocal cross gave birds of at least 

 two shades of "brown." The darker of these were females (like sire), but 1 female 

 was not of this color; 2 males and a female were of the lighter color (table 128). 



Males from the alba-risoria cross were mated to females of the risoria-alba 

 cross with the result as summarized in table 129 and more fully given in tables 



4 That is, in the F 2 generation. It is interesting that this feature of Mendclism was noted by Whitman as early 

 07. This had, however, been noted earlier, on a few forms, not only by Mendel, but by Naudin and by Darwin. 



EDITOB. 



5 The -tateinents and summaries from this point, except those marked as quotations, are made by the editor; 

 the data, of course, are those (if the author. 



