86 REIPORTS Olf INVESTIGATIONS AND PROJECTS. 



THE ONTOGENESIS OF CHARACTERISTICS. 



While each transmissible character of the organism is latent in the germ, 

 during ontogeny it gradually becomes potent and eventually acquires its adult 

 condition. Since the germinal determiner bears no resemblance to the com- 

 pleted characteristic, there must be a series of fundamental changes in ontog- 

 eny. We know that the course of ontogenesis varies according as the 

 germinal "determiner" comes from both parents or one only. In the latter 

 case the characteristic (technically denominated heterozygous) is weakened 

 and often remains at a low stage of development, even in the adult. Such 

 heterozygous characters show how ontogenesis is controlled by heredity. In 

 our publications we have repeatedly proved that heterozygous organs tend to 

 remain at a low or incomplete stage of development, in consequence of which 

 they sometimes, on the one hand, exhibit peculiar forms and, on the other, 

 obscure the Mendelian proportions in transmission. Many of these hetero- 

 zygous forms can be fully interpreted only by embryological studies. 



Again, many organs show themselves, in transmission, to be complex — 

 composed of several unit-characters or factors. It is probable that an inter- 

 pretation of this peculiar behavior will be given by embryological studies. 

 Arrangements have been made with Prof. F. R. Lillie, of the University of 

 Chicago, by which he is furnishing a trained student to work upon the devel- 

 opment of some of the hybrid organs of our pedigreed stock. In accordance 

 with this arrangement Mr. J. C. Stevenson is at present resident at this 

 Station and studying the developmental history of the heterozygous combs of 

 poultry. 



THE TRANSMISSION OF CHARACTERISTICS. 



This is the phase of the study upon which most work has been done. The 

 results have been published in a series of papers, a list of the more important 

 of which is given below. Our results, so far as published, constitute a satis- 

 factory part of the history of the remarkable development of our knowledge 

 of this subject for which the present decade will ever be famous. A brief 

 statement of the titles of the papers published by the different workers in this 

 field will give an idea of the ground covered. 



By the Director: Black sheep in the flock. Imperfection of Mendelian dom-'nance 

 in poultry hybrids. Inheritance in poultry. Heredity and Mendel's law. 

 Dominance of characteristics in poultry. Determinance of dominance. In- 

 heritance in canaries. Eye-color in man. Hair-form in man. Hair-color in 

 man. Inheritance of characteristics in poultry. 



By Dr. Shull : Latent characters in a white bean. Significance of latent characters. 

 Variations in the_ Oenotheras. The pedigree culture. Mendelian inheritance. 

 Branching and disk color of sunflowers. Flower color in Lychnis and the 

 rnullein. A new Mendelian ratio and several types of latency. The composi- 

 tion of a field of maize. A pure-line method in corn breeding. The "presence 

 and absence" hypothesis. Bursa biirsa-pastoris and Bursa heegeri, biotypes 

 and hybrids. A simple chemical device to illustrate Mendelian inheritance. 



