The increase in the width of a meteor stream with time is usually regarded as due to differences in the secular variations of the slightly different orbits of individual meteoroids. However, the ordinary differential planetary perturbations acting on different parts of an elliptical ring of meteoroids have a more important effect. Model calculations are presented for a filament-like stream that makes close approaches to Jupiter. They confirm the major importance of deformations of the stream by direct planetary perturbations that act even on a filament-like stream of zero thickness. The disturbed part of the stream takes the form of a bend, dispersing along the initial orbit and producing a significant decrease in the spatial density of the meteoric particles.