There are two distinct kinds of Andalusian fowls, one pure bred black, the other pure bred white with slight dashes of black here and there.  When these are mated, no matter which color is the father or the mother, the next or hybrid generation are always a queer mixture of black and white called by fanciers blue.  When these blues are interbred, one-quarter of their offspring will be white, which will prove to breed true ever afterwards, one-quarter will be black that will breed true, and fifty per cent. will be blue which will break up in the next generation in the very same way as before.  In this case neither white nor black character is dominant, and accordingly we have a blending of both in the first hybrid generation.

In guinea pigs, black color has been found to be dominant over white, rough coat over smooth coat, and short hair over long hair.  These remarkable results following from an experimental trial of Mendelism have stimulated hosts of investigators in all parts of the world, until now many varieties of plants and animals have been studied for many successive generations, already, building up a considerable literature dealing with the subject.

Perhaps the most extensive and exact series of experiments along this line have been carried on by Thomas Hunt Morgan and his assistants, of Columbia University.  For over five years they have been breeding the wild fruit fly (Drosophila ampelophila), during which time they have originated and observed over a hundred and twenty-five new types that breed true according to Mendel’s laws.  Every part of the body has been affected by one or another of these mutations.  The wings have been shortened, or changed in shape, or made to disappear entirely.  The eyes have been changed in color or entirely eliminated.  And each of these wonderful variations was brought about not gradually, but at a single step.

Professor Morgan grows justifiably sarcastic in contrasting these demonstrated laboratory facts with the armchair theories that have so long and so harmfully dominated biological studies.  A quotation from him will not be out of place at this point.

“I may recall in this connection that wingless flies also arose in our cultures by a single mutation.  We used to be told that wingless insects occurred on desert islands because those insects that had the best developed wings had been blown out to sea.  Whether this is true or not, I will not pretend to say; but at any rate wingless insects may also arise, not through a slow process of elimination, but at a single step....  Formerly we were taught that eyeless animals arose in caves.  This case shows that they may also arise suddenly in glass milk bottles, by a change in a single factor."[26]

[Footnote 26:  “A Critique of the Theory of Evolution,” p. 67.]