ows that illness
and death are necessary incidents in a regular sequence of
constitutional changes beginning at birth, and upon which external
circumstances have, on the whole, very small effect. In cases where
the maladies of the twins are continually alike, the clocks of their
two lives move regularly on at the same rate, governed by their
internal mechanism. When the hands approach the hour, there are
sudden clicks, followed by a whirring of wheels; the moment that
they touch it, the strokes fall. Necessitarians may derive new
arguments from the life-histories of twins.

We will now consider the converse side of our subject, which appears
to me even the more important of the two. Hitherto we have
investigated cases where the similarity at first was close, but
afterwards became less; now we will examine those in which there was
great dissimilarity at first, and will see how far an identity of
nurture in childhood and youth tended to assimilate them. As has
been already mentioned, there is a large proportion of cases of
sharply-contrasted characteristics, both of body and mind, among
twins. I have twenty such cases, given with much detail. It is a
fact that extreme dissimilarity, such as existed between Esau and
Jacob, is a no less marked peculiarity in twins of the same sex than
extreme similarity. On this curious point, and on much else in the
history of twins, I have many remarks to make, but this is not the
place to make them.

The evidence given by the twenty cases above mentioned is absolutely
accordant, so that the character of the whole may be exactly
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 till the
age of fifteen."

(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 had had any other serious illness. Both are and
have been exceedingly