Fig. 4.

Cells with Crenulated Edges. One of the relatively rare situations where circle fits do not give good membrane approach angles is when an edge has a complex geometry, such as a crenulated shape. These cells are from the amnioserosa of a Bowne's Stage 13 Drosophila embryo. In cases like this, angle estimates based on the last points along the edge tend to be considerably more accurate. However, crenulated edges have been deemed to carry little if any tension, and so the exact direction used in the angle calculations might not be that important. Furthermore, such edges, especially if relatively sparse within a given tissue, might be removed from the analysis (see text).