CHAPTER XXIII 
HEREDITY 
General Features of Heredity 
Nature of Heredity.— The constancy of species of plants 
aud animals through successive generations depends upon the 
fact that the individuals of each generation are fundamentally 
like their parents. Thus the offspring of Sweet Corn have the 
characters of Sweet Corn, and the offspring of Flint Corn have 
the characters of Flint Corn. Even when parents differing in 
one or more fundamental characters are crossed, the characters 
of both parents will appear somewhere in future generations. 
The transmission from parent to offspring of similarities in 
structure and function is heredity. But heredity means more 
than the transmission of similarities. In the study of varia- 
tions it was learned that no two individuals are alike, and hence 
offspring, although fundamentally similar and like their parents, 
always have individual differences. Thus every plant or ani- 
mal, besides resembling its parents, brothers, and sisters, has its 
own peculiar features which give it individuality. In a field of 
a given variety of Corn, although the plants have the characters 
of the parent variety, they differ in height of stalk, length and 
shape of ear, depth of kernel, time of maturing, and in many 
other ways. Most of these differences are fluctuating varia- 
tions, while some may be due to something inherited. In the 
study of heredity not only the resemblances but also the differ- 
ences must be accounted for. Heredity means the transmission 
of fundamental resemblances with differences in detail. 
The Physical Basis of Heredity. — It is obvious that parents 
do not actually transmit characters to the offspring, but trans- 
mit something that causes the characters to appear in the 
offspring. For example, a red flowered Sweet Pea does not 
transmit a red color to the flowers of its offspring, but transmits 
something through the sperm and egg that causes a red color 
535 
