Fig. 2a-d. Equatorial density contours for the standard isothermal collapse test, as calculated with code TREESPH using 13997 particles. The contour lines correspond to the logarithm of the density. The high-density value is labeled. Counterclockwise rotation is assumed. A sequence in time is presented: a (upper left) , b (upper right) , c (lower left) , and d (lower right) . The entire cloud is shown in a -c. A region of radius cm is shown in d. An essentially identical sequence was obtained using 7123 particles.