A SKETCH OF HIS LIFE 
39 
Heredity' ' remained active during life. Two of his last addresses 
(1906-1909) deal with our concepts of heredit}^ and variation. 
In these he emphasizes the fact that the nature of an organism 
is not implicit in the egg, or in the organism indeed at any time 
of its life, but that it depends on a continuous reciprocal interac- 
tion between the organism and its environment. Such interac- 
tion leads in any particular case to a result which could not be 
calculated from a knowledge, however complete, of the egg itself 
since it is dependent not only on the organism but on the action 
of the total environment. The outcome of such interaction is 
the production of individuals which are never quite alike, although 
they may resemble one another closely. The occurrence of like- 
nesses, or inheritance, and the occurrence of differences, variation, 
are thus not two processes but two views of the single process of 
reciprocal interaction. The idea that they are distinct is an error 
into which we fall through concentrating our attention at one time 
on the resemblances, and again on the differences between individ- 
uals. These considerations, he thinks, show the uselessness of 
theories which postulate an inheritance substance and explain 
individual differences as the result of various combinations of its 
particles. 
These addresses show that Brooks has in some measure shifted 
his standpoint since the time of the ''Law of Heredity." He no 
longer is in a mood to employ evolution (determinant) hypotheses 
to account for development. He now looks on the development 
of the individual, and that of races also, as epigenetic in nature. 
What will be the outcome of an individual egg depends on the 
interaction between egg and environment, not on a determinate 
mechanism in the egg. The pre-cambrian fauna has given rise 
to the living beings of to-day. But the latter were not implicit 
in the former, for with the same ancestors the course of evolution 
might have been different had the sum total of environmental 
influences been different. 
Writings on the Principles of Science. Brooks dw^elt often in 
conversation and in minor writings, and alw^ays with an earnest 
Professor H. V. Wilson, University of North Carolina. 
