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 animal remains that make it possible to fix its position in the scale of pre-historic periods with some accuracy.  Judged by this test, it is as old as the oldest of the unmistakable drift implements, the so-called Chellean (from Chelles in the department of Seine-et-Marne in France).  The jaw by itself would suggest a gorilla, being both chinless and immensely powerful.  The teeth, however, are human beyond question, and can be matched, or perhaps even in respect to certain marks of primitiveness out-matched, amongst ancient skulls of the Neanderthal order, if not also amongst modern ones from Australia.