Page:Mendel's principles of heredity; a defence.pdf/45

 manifested by the cross-bred is called "dominant" and the parental character, green, not manifested, is called recessive.

(2) The cross-bred may present some condition intermediate between the two parental forms, in which case we may still retain the term "blend" as applied to the zygote.

Such an "intermediate" may be the apparent mean between the two parental forms or be nearer to one or other in any degree. Such a case is that of a cross between a rich crimson Magenta Chinese Primrose and a clear White, giving a flower of a colour appropriately described as a "washy" magenta.

(3) The cross-bred may present some form quite different from that of either pure parent. Though, as has been stated, nothing can be predicted of an unknown case, we already know a considerable number of examples of this nature in which the mule-form approaches sometimes with great accuracy to that of a putative ancestor, near or remote. It is scarcely possible to doubt that several-though perhaps not all—of Darwin's "reversions on crossing" were of this nature.

Such a case is that of the "wild grey mouse" produced by the union of an albino tame mouse and a piebald Japanese mouse. These "reversionary" mice bred together produce the parental tame types, some other types, and "reversionary" mice again.

From what has been said it will now be clear that the applicability of the Mendelian hypothesis has, intrinsically,