THE METHODS AND SCOPE OF GENETICS 11 
given to the cycles of developments in these organisms, especially those 
phases which are comprised in development and reproduction. Of 
particular importance is a general knowledge of physiology, not so much 
on account of the direct utility which it has in the study of genetics as 
for the attitude toward life phenomena which it awakens in the student. 
Genetics, indeed, is essentially a sub-division of physiology in the broader 
sense. A knowledge of mathematics is a valuable asset because it is 
often necessary to subject the data of heredity and variation to mathe- 
matical treatment in order to interpret them properly. For the elemen- 
tary study of genetics, a knowledge of the methods of dealing with simpler 
algebraic problems is sufficient; for advanced study a knowledge of the 
differential and integral calculus is highly advantageous. Finally it 
may not be out of place to mention the fact that investigation in genetics 
is not confined to those who employ the English language. A reading 
knowledge of French and German is practically necessary for those who 
desire to pursue the subject very far. 
The Applications of Genetics.—Genetics has both scientific and prac- 
tical applications. As an example of its scientific applications, the part 
which it has played in shaping doctrines of evolution instantly comes to 
mind, for of necessity such doctrines must conform to the fundamental 
principles of genetics. The science of genetics and that of evolution are 
by their very natures constantly encroaching each upon the fields of 
research of the other. Thus experimental investigations of evolution 
are of vital interest to genetics, because they deal with the mode of 
origin of hereditary characters. Genetics, also, has its applications in 
branches of biology other than that of evolution, indeed throughout the 
entire realm of biology its influence is felt in shaping thought and direct- 
ing interpretation. There are few other sciences which possess so much 
of general interest as that of genetics. 
The practical applications of genetics are found in agriculture and 
in human affairs. Here genetics involves many things which are extra- 
biological. Thus in agriculture emphasis is placed upon the employment 
of the principles of genetics for the amelioration of plants and animals for 
man’s use. Breeding, then, may be defined as the art of improving 
plants and animals by hybridization and selection. To make effective 
progress along this line methods of testing given individuals or races, 
both with respect to fixity of type and comparative value, have been de- 
vised. The methods of attack are very much the same as those which 
are employed in the experimental study of heredity and evolution, the 
primary aim of which is merely to discover underlying principles. Eugen- 
ics is concerned with the principles of genetics in so far as they may 
be applied in the improvement of the human race; but it includes much 
that is sociological, rather than biological. The applications of the prin- 
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