The Onondaga fauna which succeeded appears to have resulted from the commingling of the resident lower Devonian fauna with new emigrants from Europe by way of the Arctic regions.
The late Devonian fauna of the interior represents the commingling of the Hamilton fauna of the eastern interior with new emigrants from the north-west, a union which was not effected until toward the close of the period.
Nevertheless, in exceptional cases modified growths, termed " grafthybrids," have been obtained which have been attributed to the commingling of the characteristics of stock and scion (see Hybridism).
Some of them are as light-skinned as Europeans, tall, robust, thin-lipped, straight-nosed, with straight black hair; others are shorter and darker in complexion, with round heads, long noses, thick lips, and scraggy limbs, indicating perhaps the commingling of more than one Semitic people.
Various experimenters, especially Fenn, have asserted that by engrafting an eye of one variety into the tuber of another, not only will adhesion take place but the new tubers will present great variety of character; this seems to be the case, but it can hardly be considered as established that the variations in question were the result of any commingling of the essences of the two varieties.