When seeing is believing: Wilhelm Roux’s misconceived fate map

Abstract

“Entwickelungsmechanik, like every new approach in science, will have to acquire its deserved status step by step. Nonetheless, posterity might well be amazed on learning that the now ruling descriptive school ignored the secure findings of Entwickelungsmechanik for a long time, until descriptive research had led to the same views, and especially that this school placed more confidence in the latter kind of findings than in the former. This will bear permanent testimony to the insufficient appreciation that those researchers had for the value of experiments.” This was Wilhelm Roux’s verdict at the end of a discussion of gastrulation and the fate map in frogs (Roux 1892, p. 441). In the preceding paragraph he had summarized his conclusions on these topics, and at the same time paved the way for the verbal showdown just quoted: “The conclusion, based on three different types of experiment, that gastrulation in the frog occurs by way of bilateral epiboly and concrescence on the lower side of the egg and that the outer face of the blastoporal lip is the site of the neural folds, is therefore so secure that its certainty could neither be increased by the consent of descriptive researchers, which is per se pleasing, nor could it be diminished by their opposition; the facts thus established must rather be viewed as the firm foundations of our knowledge of developmental processes, meaning at the same time that all views clearly incompatible with these facts can for sure be called mistaken” (Roux 1892, p. 440/41).