Table 1.

Spacing of head formation in aggregates from apical and basal tissue

	Apical tissue	Basal tissue
Heads per aggregate	2.9  ± 1.5	1.1  ± 0.7
Aggregate dimension, μm
Length	1,000  ± 269	1,285  ± 305
Width	700  ± 149	898  ± 142
Average aggregate area, μm2	19.1  × 105	31.3  × 105
Minimal head distance, μm	511  ± 248	1,237  ± 142
Area per head, μm2	6.6	28.4
Variance index	0.49	0.12

The distance between each pair of heads in 15 aggregates of each type was measured 96 h after aggregate formation. The average area of an aggregate was calculated assuming it was an ellipsoid with the two axes corresponding is the average length and width of the aggregates. The variance index is SD mean value of the minimal distance between two heads. Error is the SD.