to show that
the new environment does in some unexplained way modify the head-form
to a remarkable extent. For example, amongst the East European Jews
the head of the European-born is shorter and wider than that of the
American-born, the difference being even more marked in the second
generation of the American-born. At the same time, other European
nationalities exhibit changes of other kinds, all these changes,
however, being in the direction of a convergence towards one and the
same American type. How are we to explain these facts, supposing them
to be corroborated by more extensive studies? It would seem that we
must at any rate allow for a considerable plasticity in the head-form,
whereby it is capable of undergoing decisive alteration under the
influences of environment; not, of course, at any moment during life,
but during those early days when the growth of the head is especially
rapid. The further question whether such an acquired character can
be transmitted we need not raise again. Before passing on, however,
let this one word to the wise be uttered. If the skull can be so affected,
then what about the brain inside it? If the hereditarily long-headed
can change under suitable conditions, then what about the hereditarily
short-witted?

It remains to say a word about the types of pre-historic men as judged
by their bony remains and especially by their skulls. Naturally the
subject bristles with uncertainties.

By itself stands the so-called Pithecanthropus (Ape-man) of Java, a
regular "missing link." The top of the skull, several teeth, and a
thigh-bone, found at a certain distance from each other, are all that
we have of it or him. Dr. Dubois, their discoverer, has made out a
fairly strong case for supposing that the geological stratum in which
the remains occurred is Pliocene--that is to say, belongs to the
Tertiary epoch, to which man has not yet been traced back with any
strong probability. It must remain, however, highly doubtful whether
this is a proto-human being, or merely an ape of a type related to
the gibbon. The intermediate character is shown especially in the head
form. If an ape, Pithecanthropus had an enormous brain; if a man, he
must have verged on what we should consider idiocy.

Also standing somewhat by itself is the Heidelberg man. All that we
have of him is a well-preserved lower jaw with its teeth. It was found
more than eighty feet below the surface of the soil, in company with
anima