Weismann finds the solution in the method by which the breeder has obtained his results in artificial selection. For instance, the long-tailed variety of the domestic cock of Japan owes its existence, it is claimed, to skilful selection, and not at all to the circumstance that, at some period of the race’s history, a cock with tail-feathers six feet in length suddenly and spasmodically appeared. Weismann continues: “Now what does this mean? Simply that the hereditary diathesis, the germinal constitution (the _Anlage_) of the breed was changed in the respect in question, and our conclusion from this and numerous similar facts of artificial selection runs as follows: _by the selection alone of the plus or minus variations of a character is the constant modification of that character in the plus or minus direction determined_. Obviously the hereditary _diminution_ of a part is also effected by the simple selection of the individuals in each generation possessing the smallest parts, as is proved, for example, by the tiny bills and feet of numerous breeds of doves. We may assert, therefore, in general terms: a definitely directed progressive variation of a given part is produced by continued selection in that definite direction. This is no hypothesis, but a direct inference from the facts and may also be expressed as follows: _by a selection of the kind referred to the germ is progressively modified in a manner corresponding with the production of a definitely directed progressive variation of the part_.” So far there is nothing essentially new offered, since Darwin often tacitly recognized that the standard of variation could be raised in this way, and in some places he has made definite statements that this will take place. Weismann thinks that after each selection, fluctuation will then occur around a higher average (mode). He says “that this is a fact,” and is proved by the case of the Japanese cock. It need scarcely be pointed out that it is an assumption, based on what is supposed to have taken place in this bird, and is not a “fact.”