ing chaos that it produces. When characters such as blue eyes 
were common to both parent and child, they called it an inherited 
character. But often brown-eyed parents had both blue and 
brown-eyed children. Then chaos reigned again. Theories in- 
numerable were propounded to account for the manner in which 
characters arose, and were or were not inherited. The wildest 
superstitions were common. Strawberry-like birthmarks ap- 
peared on children because the mother had seen or dreamed of 
strawberries preceding its birth. Hours were spent before statues 
and beautiful paintings, so that the unborn child might be beau- 
tiful. Experiments by learned men were few and far between, and 
resulted only in more theory, or in collections of interesting but 
isolated facts. Heredity, says an old writer, is a curious collec- 
tion of uncorrelated facts with no laws. 
Then came Gregor Mendel, the Austrian monk, with his pre- 
cise mathematical mind; and, with studied care, he thought out 
some experiments that might prove helpful in bringing order out 
chaos. He carefully selected his material, made sure b} r actual 
tests that it bred true to certain well defined characters, and then 
proceeded with some crossing experiments between varieties which 
differed from each other in one or more of these tested, true- 
breeding characters. When a tall pea was crossed with a dwarf 
pea plant, the progeny were all tall, and when the seed of these 
tails were planted, tall plants and dwarf plants appeared in the 
proportion of three tails to one dwarf. All the dwarfs and ap- 
proximately one-third of the tall plants bred true respectively to 
dwarfness and tallness, but the remaining tall plants produced 
seed which gave again the ratio of three tall plants to one dwarf. 
From extensive experiments tried since, we have every reason to 
believe that two-thirds of the tails from such a cross after the 
first generation would always produce dwarfs and tails in approx- 
imately the three to one ratio. Other characters, such as green 
and yellow seed, green and yellow foliage, round and flat stems, 
were tested by Mendel in this manner, and the results they gave 
agreed with those obtained in the first example. Next he crossed 
varieties which bred true to two of these characters. When tall, 
yellow-seeded peas were crossed with dwarf, green-seeded peas, 
the offspring were all uniformly tall and yellow-seeded. When 
seed of these were sown, four kinds of pea plants appeared, and 
in approximately the following ratio: nine tall yellow- seeded, 
threetall green-seeded, three dwarf yellow-seeded, and one dwarf 
green-seeded. Without bothering with further details, it is only 
necessary to say that from these and other results he formulated 
the first clear law of heredity that is extant— the so-called law of 
segregation. He found that different characters appeared to act 
as units in heredity, and that these could be transferred from one 
