the nature of the stem (fasciated or normal). After satisfying 
himself as to the manner in which a single pair of characters is 
inherited, he crossed varieties which bred true to two of these 
differentiating characters. When tall, yellow-seeded peas were 
crossed with dwarf green-seeded peas, the offspring were all uni- 
formly tall and yellow-seeded. When seed of these were sow r n, 
four kinds of progeny were produced in approximately the follow- 
ing ratio: nine tall yellow-seeded, three tall green-seeded, three 
dwarf yellow-seeded, and one dwarf green-seeded. Out of each 
group a definite proportion bred true to both characters, — in the 
first, approximately one in every nine; in each of the next two 
groups, one in every three, and in the last group, the dwarf 
green-seeded plants all bred true. 
Space is too short to deal with the character of the remaining 
offspring in the other three groups except to say that a general law 
was followed. Although still more elaborate experiments were 
made, extending over a period of eight years in which varieties 
differing in three sets of characters were crossed, nothing of an 
exceptional nature was discovered. So from these and other re- 
sults, Mendel formulated the first clear law of heredity extant— 
the so-called law of segregation. He found that the different char- 
acters in his peas appeared to be inherited as units, and that such 
a character as tallness could be transferred from a green-seeded 
variety to one with yellow seeds independently of the other char- 
acters such as green seeds, with which it had hitherto been assoc- 
iated. The next step naturally then was to make a general appli- 
cation of the law —in other words — to consider all animals and 
plants as being made up of many independent character mater- 
ials, each of which could be separately inherited. But, as with 
most pioneers, scant attention was given to the laws and discov- 
eries which he published in 1865 in the transactions of the local sci- 
entific society of Briinn, and after the thirty-five years that his 
work remained unnoticed, Mendel died, a disappointed and dis- 
couraged old man. 
In 1900, three Europeon botanists— Correns, deVries and von 
Tschermak — experimenting along similar lines, each independent- 
ly rediscovered the law, and Mendel’s long forgotten and neglect- 
ed account was resurrected and once more brought to public notice. 
This time a hearing was gladly granted, a new science grew up, 
and general interest in plant and animal breeding spread with 
cyclone rapidity. The study of heredity became a fad which reached 
its height in the so-called science of eugenics. Through Mendel’s 
work, and the encouragement derived from his discoveiies, the 
nature of variation and heredity and their relation to environment is 
beginningto be understood. Variation can now be classified from 
the standpoint of cause, instead of only by form or by appearance. 
When three varieties of beans, each breeding true to -white seed, 
are crossed with a single variety of bean breedingtrueto red coats 
and in each cross, a different colored progeny is obtained (black, 
dark blue with white specks, brown gray) , we are not forced back 
to the old time chaos. Thanks to Mendel’s methods and concep- 
tion, we have a key by which we are able to see law and order in 
this seemingly contradictory result. And what is far more im- 
portant, we are able to repeat this performance again and again 
with the same results. 
Since 1900 many important modifications of Mendel’s original 
conception have come about, as might be expected when scores of 
experimenters are engrossed in the experimental study of hun- 
dreds of different plant and animal forms. Important among these 
modifications is our conception of what constitutes a character. 
We have been forced to drop the vague meaning attached to this 
term by the older biologists and adopt the usage of the chemists 
