388 r. H. DANFORTH 



the contents recorded. Since the eggs were candled frequently 

 many embryos were obtained only a few days after death and 

 consequently in a good state of preservation. Very few of 

 the dead embryos were found to be too macerated to afford the 

 desu-ed data. Some living embryos were purposely taken. 

 For the sake of brevity, data obtained from eggs laid during 

 the periods of alcohol treatment will be referred to as A, those 

 from eggs laid in the control periods as C. Each experiment, 

 therefore, has an A and a C subdivision. In experiments 1, 2, 

 and 3 the heterozygous individuals were males, in 4 they were 

 females. 



The characteristics tested for their possible response to al- 

 cohol vapor were brachydactyly, Polydactyly, and color. The 

 presence or absence of booting (feathers on the tarsi) and the 

 apparent form of the comb were also recorded, but the former 

 has been found to be only another manifestation of the factor 

 which produces brachydactyly, while chicks that have been 

 allowed to develop have shown that comb form cannot, in the 

 material used, be accurately determined in embryos and young 

 specimens. Sex was not recorded. The nature of the pe- 

 culiarities under investigation may be brieflj- indicated. 



Brachydactyly is a condition described by Danforth ('19) 

 which manifests itself in a more or less pronounced shorten- 

 ing of digit IV of the foot. This shortening involves the length, 

 and in extreme cases the number, of bones in the digit. Nearly 

 all brachydactyl birds are booted, but there is a small percent- 

 age that has unfeathered tarsi. Conversely, there is an occa- 

 sional individual with feather tarsi w^hich is not brachydactj^l. 

 Breeding experiments have seemed to establish the fact that 

 these conditions are interchangeable from the point of view of 

 heredity or, in other words, that they merely represent different 

 expressions of one and the same underlying cause. Conse- 

 quently, a single term may be used to cover all of these phae- 

 notypic manifestations, although it must be borne in mind that 

 in a certain small number of cases the w^ord 'brachydactyl' 

 used in this sense is not strictly literal. Brachydactyly may 

 be recognized after about the tenth day of incubation. The 



