METHOD AND MATERIAL. 5 



B. METHOD AND MATERIAL. 



To answer in the shortest time the foregoing questions about inheritance 

 it was necessary to use some rapid and fecund breeder and to interbreed 

 both varieties and species. But species-breeding is slower and more diffi- 

 cult and not more important than breeding races ; for while on the one hand 

 it may be urged that races are artificial, having arisen under domestication, 

 on the other hand hybridization between established species probably plays 

 little part in nature. What must occur again and again in nature is the 

 mating of a mutation or newly arisen race with the parent species.*' It has 

 been urged that, in such cases, the rare mutation must be swamped by 

 intercrossing with the numerous representatives of the species. But if new 

 characters do not blend in breeding we can see that a new characteristic 

 once arisen may not be swamped. Consequently the study of inheritance 

 in races assumes first importance, and domestic races afford the best material 

 for such study. 



Again, if we accept the doctrine that man is a single species, all the mo- 

 mentous questions of human inheritance are questions of race inheritance. 

 The outcome of such an admixture of races as is going on in America is a 

 question of race inheritance. The offspring of a man and a woman having 

 one or more diverse characteristics will follow the laws deduced from a study 

 of crossed races. These are practical problems of human evolution, and 

 experiments made with domesticated races can throw light upon them. 



The main material utilized has been, as stated, poultry. Poultry offer 

 these great advantages : That they are easily bred in great numbers, that two 

 generations can be reared to maturity in a year, that they stand much/ 

 inbreeding without loss of fertility, and that the number of well-defined] 

 characteristics in the group is very great. 



In my experiments I have kept 29 pens, each with its cock and one or 

 more hens. To separate the eggs of the different females, trap nests were 

 used in the later experiments to hold the hen until she is released. Her 

 number is read and written, with date, upon the egg. Before placing the 

 eggs in the incubator, a list is made of them. Before hatching, eggs of 

 each of the different parentages are separated into a compartment by them- 

 selves, so that the exact parents of each chick may be known. A legband 

 •is applied to the chick the moment it is removed from the pedigree tray of 

 the incubator. By these means I have gained in one year 1,500 offspring 

 derived from known parents, and have reared about 500 of them to a period 

 when their adult plumage characters were distinguishable. For keeping 

 records I have used a field pocketbook and a day book at my work-table, 

 "lyoose leaf" forms were used for the description of each of the stock, for 

 its egg record, for ^ q^art of its plumage, and for its photographs. Finally 

 the results of each set of experiments are kept in a large book, posted nearly 

 to date. 



