130 TORREYA 



mind gave the new science of genetics its sharply accurate terminology. In- 

 herited variations involve permanent changes in the genotype while the im- 

 permanent ones involve changes in reaction of this permanent genotype under 

 changed environmental experiences. Only genotypic changes can have im- 

 mediate and direct importance for evolutionary progress, although the capacity 

 of a single genotype to react in different ways in response to changed environ- 

 ments may be of crucial importance in determining the survival of the genotype 

 in question in relation to its competitors in the "struggle for existence." 



Because of certain technical advantages of plants for genetical studies, 

 especially the facility they have for self-fertilization, Alendel's laws were 

 worked out with garden peas, and all of the three nearly simultaneously pub- 

 lished papers of De Vries, Correns and Tschermak were based on experi- 

 ments with plants ; but work by L. Cuenot with mice, of Bateson and his dis- 

 tinguished coterie of collaborators with poultry and canaries, of Long with 

 snails, of Castle with guinea-pigs, rats and rabbits and Davenport with poultry, 

 canaries and with studies of human families, quickly showed that animals as 

 well as plants follow identical patterns of genetical behavior. 



The simplicity of the pedigree-culture methods and the fundamental im- 

 portance of the facts and principles to be derived from the utilization of these 

 methods, resulted in a very prompt participation of many investigators who 

 in many cases abandoned for the time being the important fields of their pre- 

 vious interest to become the founders of the science of Genetics as we know 

 it today. I have already mentioned in this connection the plant physiologist 

 Johannsen and the animal morphologist and comparative anatomist Bateson. 

 To these should be added the statisticians, Galton, Pearson and Davenport, 

 embryologists such as ]\lorgan and Conklin, and cytologists like E. B. Wilson, 

 C. E. McClung and Calvin Bridges, to mention only a few of the more out- 

 standing examples. 



In this way there has grown a body of knowledge of plant and animal 

 organization of astounding magnitude in the brief period of four decades. 

 There has also been demonstrated a meticulous consistency of all of the phe- 

 nomena which have been brought to light by these methods applied to both 

 plants and animals. This consistency stresses a closeness of kinship of all living 

 things, which hardly could have been dreamed of before the demonstration of 

 the genes as the elements of organization of living matter. 



The genetical approach has served to bring into harmony many phenomena 

 of plant and animal organization and behavior which previously had had 

 seemingly few points in common. For example the whole field of sex relation- 

 ship has been greatly clarified through recognition of its basic relationship to 

 genetical phenomena. ]\Iendelian heredity was soon recognized as the product 

 of the two critical phenomena which lie at the base of all sex, namely, the phe- 

 nomena of diploidization through the union of egg and sperm, and haploidiza- 



