ge, notwithstanding very different conditions of life; in others a
severe disease was sufficient to account for some change noticed. Other
dissimilarity that developed, Galton had reason to believe, was due to
the development of inborn characters that appeared late in life. He
therefore felt justified in broadly concluding "that the only
circumstance, within the range of those by which persons of similar
conditions of life are affected, that is capable of producing a marked
effect on the character of adults, is illness or some accident which
causes physical infirmity. The twins who closely resembled each other in
childhood and early youth, and were reared under not very dissimilar
conditions, either grow unlike through the development of natural [that
is, inherited] characteristics which had lain dormant at first, or else
they continue their lives, keeping time like two watches, hardly to be
thrown out of accord except by some physical jar."

Here was a distinct failure of nurture to modify the inborn nature. We
next consider the ordinary twins who were unlike from the start. Galton
had twenty such cases, given with much detail. "It is a fact," he
observes, "that extreme dissimilarity, such as existed between Jacob and
Esau, is a no less marked peculiarity of twins of the same sex than
extreme similarity." The character of the evidence as a whole may be
fairly conveyed by a few quotations:

(1) One parent says: "They have had _exactly the same nurture_ from
their birth up to the present time; they are both perfectly healthy and
strong, yet they are otherwise as dissimilar as two boys could be,
physically, mentally, and in their emotional nature."

(2) "I can answer most decidedly that the twins have been perfectly
dissimilar in character, habits, and likeness from the moment of their
birth to the present time, though they were nursed by the same woman,
went to school together, and were never separated until the age of
thirteen."

(3) "They have never been separated, never the least differently treated
in food, clothing, or education; both teethed at the same time, both had
measles, whooping cough, and scarlatina at the same time, and neither
has had any other serious illness. Both are and have been exceedingly
healthy, and have good abilities; yet they differ as much from each
other in mental cast as any one of my family differs from another."

(4) "Very dissimilar in mind and body; the one is quiet, retiring, and