3 
connection with those variations which are necessarily and 
inevitably associated with sexual reproduction. These pro 
vide materials for a considerable amount of modification, 
and it is easy to see why this should of necessity be the 
case. At the outset it is safe to say of all things animate 
and inanimate that— 
“No compound of this earthly ball 
Is like another, all in all.’' 
Hence the two parents are not alike to begin with. 
And it seldom happens that the offspring resemble father 
and mother in exactly equal degree : one “ favours ” the 
father, another the mother. In these circumstances we 
need not be surprised to find that the strongest family 
likeness does not prevent the occurrence of individual 
differences. 
“ Facies non omnibus una 
Nec diversa tamen ; qualem decet esse sororum.” 
Between those who most closely resemble one another 
there is at least, as Mr. Wallace points out, an “ absence 
of identity.” Nor is this all. The offspring are not only 
compounds in ever-varying proportions of father and 
mother: they also tend to resemble, more or less, the 
grandfather or the grandmother, or some more remote 
ancestor, by the principle known as atavism or rever 
sion to an ancestral type. As Oliver Wendell Holmes 
says, in his witty fashion :— 
“At one moment we detect the look, at another the tone of 
voice, at another some characteristic movement of this or that 
ancestor, in our relations or others. There are times when our 
friends do not act like themselves, but apparently in obedience to 
some other law than that of their own proper nature. We all do 
things both awake and asleep which surprise us. Perhaps we have 
co-tenants in this house we live in. No less than eight distinct 
personalities are said to have co-existed in a single female men 
tioned by an ancient physician of unimpeachable authority. In this