76 REPORTS ON INVESTIGATIONS AND PROJECTS. 



THE ONTOGENESIS OF CHARACTERISTICS. 



In the studies on the comb, tail, and feet of fowl conclusions were reached 

 concerning dominance based on the relative frequency of occurrence of the 

 dominant characteristic and its opposite in the second hybrid and subsequent 

 generations. To test the hypothesis that dominance is due to the presence of 

 something, while recessiveness is due to its absence, it was desirable to have 

 studies made on the embryological development of the characteristics. For 

 instance, there are "rumpless" fowl and the behavior of rumplessness in 

 breeding suggests the hypothesis that this defect is due to a something that 

 stops the normal development of the tail. Does the development of the tail 

 region in the rumpless fowl give evidence on this point? Miss Elizabeth S. 

 Lum has started an investigation of this point and some time will be required 

 to complete it. It is significant that the rumpless fowl at first has a pointed 

 tail, but its development seems to be prematurely interrupted as though there 

 were present a local inhibitor of development. 



Similarly the evidence from heredity indicated that the webbing (syn- 

 dactylism) in the foot of some poultry is due to the presence of a factor 

 absent in birds with non-webbed feet. The study of the developmental his- 

 tory of this characteristic has been begun by Mr. E. Carleton MacDowell, 

 and is calculated to throw light on the process by which distinct digits are 

 formed from the primitive paddle-like tip of the appendage. The extended 

 studies that we have made on the inheritance of the varied forms of the 

 comb of fowl raised so many questions concerning the factors involved in the 

 development of the comb that we were glad to supply Mr. J. C. Stephenson, 

 of the University of Chicago, with a variety of types of comb for the study 

 of the embryology of this organ, upon which a report is soon to be expected. 



THE TRANSMISSION OF CHARACTERISTICS. 



This subject, heredity, has received more attention from us than any other, 

 and the longer it is studied the more the subject develops. The two most 

 voluminous publications of the year, that of Mr. Roswell Hill Johnson and 

 my own, deal with this topic, and some account of their scope and general 

 conclusions may be given. Mr. Johnson's paper is entitled "Determinate 

 evolution in the color-pattern of the lady-beetles." These beetles are quite 

 undomesticated and much labor was necessary to make them breed abun- 

 dantly in captivity, the more so as most of them require living insects as 

 food; nevertheless Mr. Johnson was very successful. He concludes that 

 segregation of characters occurs in the hybridization of these beetles, but is 

 not always clean-cut, and that dominance is irregular and variable in degree. 

 He introduces the term "preponderance" to denote the fact of frequent ex- 

 cess in numbers of extracted "dominants." 



Dr. F. E. Lutz, whose paper on heredity of characteristics in the fruit-fly 

 has been submitted for publication, likewise finds "dominance" very irregu- 

 lar, and Dr. Shull has shown how in many cases it may be difficult or impos- 

 sible to detect. 



