10 GENETICS IN RELATION TO AGRICULTURE 
The Method of Experimental Morphology.—Under the heading 
morphology, we include those particular phases of development which 
are designated by the terms, ontogeny and embryology. The method 
of experimental morphology has for its task the solution of the problem 
of the development of the individual as it is related to problems of 
variation and heredity. The aim of this method is to determine how 
the characters of the adult become patent as development proceeds, the 
broad question of the origin of complexities within organisms. 
In the Mendelian method, the formal relations which exist between 
hereditary elements are dealt with, particularly their relations in dis- 
tribution and recombination. The characters of the adult organism are 
for the most part the basis of judgment. In spite of the general truth of 
this statement, however, Mendelian analysis has in many cases extended 
into the field of the physiological relations which exist between hereditary 
elements, not merely with regard to contrasted homologous hereditary 
. determiners, but with regard to the physiological relations existing in 
development between entire sets of hereditary elements, and at times 
even between these and definite factors of environment. But for the 
most part the solution of such problems depends upon thorough experi- 
mental study of development in individuals of known genetic constitution. 
This portion of the problem remains almost untouched. If development 
be thought of as a series of successive physico-chemical reactions, the 
complexity of the problem may easily be judged. Certain of the simpler 
features of it, however, have been attacked and the results of these 
preliminary studies have indicated still other modes of approach, so that 
we may expect that when geneticists come to appreciate the light which 
may be thrown upon heredity by the experimental investigation of 
development, research in this field will be greatly stimulated. Already 
as Jennings has pointed out the main features of the process of develop- 
ment are clearly indicated; the hereditary elements of the chromosomes 
remain the same in each cell, the reactions and functions of any cell 
depend upon this chromatin system working in conjunction with the 
cytoplasmic matrix in which it is located. From this fact may be drawn 
the broad conclusion that differentiation within the individual depends 
upon cytoplasm differentiation. The difficulty of the question of how 
and why should not deter investigation. 
Prerequisites for Genetics.—The foregoing discussion of modes of 
research in genetics should indicate something as to the nature of the 
working equipment necessary for a study of the science. Since genetics 
is a biological science, intelligent study of it presupposes a thorough 
grounding in general biology such as is given in foundation courses in 
botany and in zoology. Inasmuch as practically all domesticated plants 
and animals belong to the higher orders, particular attention should be 
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