REPORT OF THE PRESIDENT, 1923. 9 



part due to new conditions or influences, corresponds to the distinction 

 between a process in which the nature of each series of individuals is 

 predetermined and one in which the direction of modification may be 

 turned away shghtly from the path marked out by heredity. Accord- 

 ing to the first process, growth or evolution in the life world may work 

 out its own course. Under the second possibiUty the characteristics of 

 an individual are determined in the main by its ancestry with the 

 added chance of modification, depending upon special influences, 

 internal or external, affecting the cells from which the individual 

 originates. One condition gives a life world with relatively narrow 

 limits for advance; the other makes life more clearly plastic and opens 

 a wider range of opportunity for directed growth or evolution. 



The researches of the Division of Ecology, devoted to consideration 

 of relation of the life process to the biological and physical environment, 

 involve the problem of life succession or growth or evolution seen from 

 a point of view rather different from that of the geneticist. The results 

 of the ecologist's investigations contribute toward the solution of our 

 growth problem certain elements which are of great importance in any 

 attempt to estimate the nature of biological succession. The mutual 

 support of the geneticists and ecologists through the machinery offered 

 by the Institution is certain to give us an understanding of some of 

 the critical phenomena bearing upon evolution, such as will be needed 

 in the next stage of advance in biology. In this division several sig- 

 nificant contributions have been made this year, among which is the 

 important publication by Hall and Clements on ''The phylogenetic 

 method in taxonomy." 



Since the death in 1922 of Alfred G. Mayor, head of our Depart- 

 ment of Marine Biology, we have attempted to advance to their 

 natural culmination the studies initiated under 

 BkSo*^^ Dr. Mayor's guidance. We have also made the 



Marine Biological Laboratory at the Dry Tortugas 

 available to those of Dr. Mayor's associates desiring the advantages 

 of this favorable collecting-ground, together with equipment and 

 field assistance for biological research. In the course of the past year 

 the President visited the Tortugas Laboratory, as also a number of the 

 sites for biological stations in the Gulf region and on the east coast of 

 Florida. A careful study of the possible needs for continuation of the 

 work in marine biology has been carried out through conferences with 

 many of the leading biologists in this country. 



The inmaediate future of our work in marine biology depends on the 

 urgency of need for well-organized investigations in fundamental 

 questions requiring an equipment such as is available at our Laboratory. 



