DEPARTMENT OF EXPERIMENTAL EVOLUTION. 



17 



(7) Purity of extracted recessives and dominants. 



(8) Creation of new "pure" races. 



(9) Fixation of characters by contamination. 



(10) Reversion, or the appearance in hybrids of ancestral characters. 



(11) Transfer of qualities from one sex to the other. 



(12) Comparative effect of reciprocal crosses. 



(13) Effect of inbreeding- 



Heredity in Canary Birds. — C. B. Davenport. 



Of cage-birds, 94 canaries and various hybrids between canaries and 

 finches were hatched. Song sparrows, Java sparrows, and Australian grass 

 parakeets were only partially successfully bred. It is proposed to extend this 

 work slightly. Meanwhile a report on the work done so far is in press. The 

 principal result, apart from determining the presence in these birds of Men- 

 delian unit-characters, is the discovery that the yellow canary bears a mottling 

 factor. This accounts for the mottling of the offspring of the yellow and 

 green canaries and also for the extraordinary variability of hybrids between 

 the canary and other species of finches. Also, a simple explanation is given 

 for a case of "reversion" in canary hybrids referred to by Darwin. 



Breeding Strains of Plants. — George H. Shnll. 



The cultures designed to elucidate the laws of variabiHty and inheritance 

 of characters in plants have materially forwarded the solution of the problems 

 outlined in previous reports. In addition to those problems, the attempt is 

 being made to analyze the complex color variations in the Shirley poppy, a 

 garden derivative of the little red Papaver rha^as of the English fields. For 

 this purpose careful descriptions of over 50 specimens were recorded by 

 means of a spectrum scale, and all were crossed upon a single mother plant. 

 Self-fertilization, which supplies the most advantageous method in many 

 cases of this kind, is impracticable in the case of the Shirley poppy, because 

 it is rare that any good seed is secured by this means. 



The scope and extent of the pedigree-culture work with plants may be 

 summed up in the following tabulated list of species, which have been under 

 observation during the year: 



