This note discusses an estimator for the slope of a straight line as proposed by Werman and Geyzel ("Fitting a second degree curve in the presence of error", ibid., vol. 17, no. 2, p. 207-11, 1995). By computing its frequency distribution, the authors demonstrate that the estimator is a unreliable; it possesses neither a first nor a second moment. Application leads therefore to completely erratic outcomes. Werman replies that the problem is well known, and describes the methods taken to overcome it.

To extend computer-aided three-dimensional reconstruction of (microscopic) biological structures to complex topologies, a number of specially developed contour algorithms are employed to generate hidden-line displays of user-specified selections from a dual-access relational database. The database consists of piles of automatically aligned contours from either handtraced or automatically detected surface boundaries in a series of parallel cross-sections that result from the slicing of an embedded, stained biologic structure with alignment references. A video-tape with animation sequences generated with this package will be shown during the conference.

A numerical method is presented to close the truncated Fourier descriptor presentation of a closed curve.