Professor Weldon refers to both Crampe and von Guaita, whose results show an essential harmony in the fact that both found albino an obvious recessive, pure almost without exception, while the coloured forms show various phenomena of dominance. Both found heterozygous colour-types. He then searches for something that looks like a contradiction. Of this there is no lack in the works of Johann von Fischer (11)—an authority of a very different character—whom he quotes in the following few words:
“In both rats and mice von Fischer says that piebald rats crossed with albino varieties of their species, give piebald young if the father only is piebald, white young if the mother only is piebald.”
But this is doing small justice to the completeness of Johann von Fischer’s statement, which is indeed a proposition of much more amazing import.
That investigator in fact began by a study of the cross between the albino Ferret and the Polecat, as a means of testing whether they were two species or merely varieties. The cross, he found, was in colour and form a blend of the parental types. Therefore, he declares, the Ferret and the Polecat are two distinct species, because, “as everybody ought to know,”
“The result of a cross between albino and normal [of one species] is always a constant one, namely an offspring like the father at least in colour[135],”
whereas in crosses (between species) this is not the case.
And again, after reciting that the Ferret-Polecat crosses gave intermediates, he states:
“But all this is not the case in crosses between albinos and normal animals within the species, in which always and without any exception the young resemble the father in colour[136].”
These are admirable illustrations of what is meant by a “universal” proposition. But von Fischer doesn’t stop here. He proceeds to give a collection of evidence in proof of this truth which he says “ought to be known to everyone.” He has observed the fact in regard to albino mole, albino shrew (Sorex araneus), melanic squirrel (Sciurus vulgaris), albino ground-squirrel (Hypudaeus terrestris), albino hamster, albino rats, albino mice, piebald (grey-and-white or black-and-white) mice and rats, partially albino sparrow, and we are even presented with two cases in Man. No single exception was known to von Fischer[137].
In his subsequent paper von Fischer declares that from matings of rats in which the mothers were grey and the fathers albino he bred 2017 pure albinos; and from albino mothers and grey fathers 3830 normal greys. “Not a single individual varied in any respect, or was in any way intermediate.”