DEPARTMENT OE EXPERIMENTAL EVOLUTION. 77 



The "Inheritance of characteristics in domestic fowl" is a continuation of 

 "Inheritance in poultry." The principal results are a demonstration of varia- 

 tion in the degree of dominance (illustrated by the relative proportion of the 

 two elements in the hybrid between single and V comb) and of the inherit- 

 ance of such degree. This variation in dominance shows itself also in poly- 

 dactylism, syndactylism, and rumplessness. A study is also made of some 

 characters that seem to blend, such as foot-feathering and nostril-height, and 

 it is shown that even in these cases there is evidence of segregation, so that 

 the probability is strengthened that segregation is never absent in inheritance 

 and Galton's three types of heredity are merely different forms of segregated 

 heredity. A case of apparent failure to transmit a character (comb-lop) is 

 found. This adds another to the two or three previously known cases of 

 non-inheritance of a right and left character. The complex factors of the 

 plumage colors of several varieties of poultry were disentangled and simple 

 formulae discovered by which the proportions of any color in a given hybrid 

 mating can be predicted. 



Progress has been made in the analysis of the method of inheritance of 

 sex by breeding over 200 families of a species of Lychnis, which affords 

 male, female, and hermaphrodite individuals. To this problem Dr. Shull is 

 devoting a large part of his attention. 



The studies on inheritance of human characteristics have been greatly 

 developed, and a booklet on "Eugenics," written by the Director, has awak- 

 ened interest in the improvement of mankind by better breeding and has led 

 to the establishment during the year of a eugenics record office at Cold 

 Spring Harbor, in connection with the American Breeders' Association and 

 supported from an outside source. 



The studies on the relation of chromosomes to heredity, carried on by 

 Miss Lutz, are yielding results of increasing interest. 



THE MODIFICATION OE CHARACTERISTICS. 



The results of Mr. R. H. Johnson's experiments in subjecting larvae of 

 lady-beetles to variations in temperature have been published. By subjecting 

 larvae to a low temperature new lines and spots of pigment appeared on the 

 elytra. The study of the inheritableness of this changed pattern was not 

 completed. 



The relation of general vegetative vigor and variability to pure-line breed- 

 ing in corn and to hybridization between pure lines has been further investi- 

 gated by Dr. Shull and his earlier results sustained. 



The Department is cooperating with Prof. H. H. Donaldson, of the Wistar 

 Institute of Anatomy and Biology, in an experiment on albino rats. As 

 Professor Donaldson has shown, albino rats have a nervous system that is 

 much smaller in proportion to the weight of the entire body than that of 

 Norway rats, and it seems probable that this is due to the fact that they have 

 always been reared in cages. It was desired to set them at liberty in a place 

 whence they could not escape. Accordingly it was decided to employ Goose 



