30 
R. Ruggles Gates. 
subsequent advances have been enormous. Many new sciences, 
such as cytology, bio-chemistry and ecology, have come into 
existence, and have made possible an insight into organic structure, 
constitution and relationship which was undreamed of even half a 
century ago. 
Just as it is rash to attempt to interpret heredity and variation 
without a knowledge of the microscopic details of cell and nuclear 
structure or the physiology of hormones, chalones and enzymes ; 
so it is equally unsafe to explain many questions of distribution 
without an intimate knowledge of the ecology and physiology of the 
organisms concerned. The burden of knowledge laid upon the 
modern evolutionist is thus so great that no one measures up to the 
possibilities, and it becomes necessary for the worker in one field 
to obtain second-hand his knowledge of the results in other fields. 
But it is none the less incumbent upon him to utilize these results 
intelligently if evolutionary science is to advance. 
This is particularly true of such disciplines as the experimental 
study of heredity and the investigation of cell and nuclear structure, 
which had their historical origin in complete independence of each 
other and have since converged so closely that their results are 
mutually interwoven. Rarely in the history of science has such a 
remarkable convergence taken place. Modern genetics represents 
a synthesis of these two sciences into one. Many genera of plants 
and animals have now been attacked from both aspects, that of 
breeding experiments and that of cell structure, with mutually 
beneficial results; and it is too obvious to need pointing out that 
the present position of genetics, both in our knowledge of heredity 
and of variation, could not possibly have been attained without 
such combined studies. (Enothera and Drosophila are conspicuous 
examples but there are many others in the recent literature. In 
future these two sciences cannot afford to stand alone, but must 
derive mutual support from each other. Interpretations of breeding 
results, especially those introducing new complications, which ignore 
or run counter to well known cytological facts, will have little chance 
of acceptance. Cytology in its turn will greatly benefit by more 
comparative studies of related races and species, such as are now 
being made in a number of plant and animal forms. In such way 
it is to be expected that a synthetic understanding of genetic 
phenomena from the combined structural and functional or 
physiological aspects may be attained, 
