The Chiasmatype Theory of Janssens

Abstract

The author discusses the theory under the following headings: Do chiasms really occur; difficulties of interpreting microscopical observations; manner of splitting of chromosomes; origin of chromosome forms; cross-shaped chromosomes; ring chromosomes; inadequacy of evidence for chiasmatypy; nature of the chromatids. The conclusions are, considering the evidence in the grasshoppers, that Janssens'' observations and interpretations were faulty and that there is no cytologic evidence that chiasmatypy really occurs.