A Critique of the Theory of Evolution

by Thomas Hunt Morgan

Fig. 86. Cross of pigeon with normal tail P₁ and fantail P₁; F₁, bird below.

Fig. 87. Cross of normal and fantail pigeons. (See Fig. 86.) The F₂ range is wider than that of F₁. The normal grand-parental type of 12 feathers was recovered in F₂ but the higher numbers characteristic of fantails were not recovered.

The preceding account attempts to point out how I should prefer to interpret the problem of selection in the light of the most recent work on breeding. But I would give a very incomplete account of the whole situation if I neglected to include some important work which has led some of my fellow-workers to a very different conclusion.

Fig. 88. Scheme to show classes of hooded rats used by Castle. (After Castle.)

Castle in particular is the champion of a view based on his results with hooded rats. Starting with individuals which have a narrow black stripe down the back he selected for a narrower stripe in one direction and for a