In 1903 the well-known Dutch astronomer Kapteyn published a paper in which he discussed statistical methods which he thought would be relevant for biologists. His motivation was the 1895 paper of Pearson on skew-frequency curves. Kapteyn had concluded that the theory was open to grave objections and was not adapted to nonmathematical readers. He was then led to an independent investigation of the subject. This publication would lead to a heated dialogue between Kapteyn and Pearson, in which they accused each other of inappropriate starting points, of plagiarism and of making serious mathematical mistakes. This article evaluates these claims. In addition, Kapteyn's struggle to make his work accessible to biologists is discussed. © 2009 The Author. Journal compilation © 2009 International Statistical Institute. Published by Blackwell Publishing Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street, Malden, MA 02148, USA.