Table 2.

Cell numbers in each segment of the anterior and posterior tubules

	Initial segment	Transitional segment	Main segment	Lower tubule	Total
Principal cells
Anterior tubules	22 ± 0.2 (178)	22 ± 0.3 (177)	77  ±  1.2 (73)	25  ±  0.4 (86)	145  ±  0.9 (123)
Posterior tubules	3.6 ± 0.1 (59)	3.4 ± 0.1 (59)	75  ±  2.4 (13)	23  ±  0.4 (82)	111  ±  1.0 (120)
Stellate cells
Anterior tubules	13 ± 0.2 (93)		20	0	33  ±  0.4 (77)
Posterior tubules	2.3 ± 1 (79)		20	0	22  ±  0.4 (59)

Lines c825, c507, c232, c724, and c649 were used for this analysis. The lower tubule runs to the bifurcation of the ureter. The ureter is not included in the counting, because of the heterogeneity of cell types it comprises. By inspection, stellate cells were known to be distributed evenly between initial and transitional segments, but because of the lack of a single line, which distinguished between stellate cells of the two domains, the two are not formally separated. Stellate cells of main segment were calculated by subtraction of cell numbers from line c649, which specifically marked stellate cells of initial and transitional segments, from totals obtained from lines c710 or c724, which marked all stellate cells. Stellate cells were not observed proximal to the main/lower tubule boundary (Fig. 4D; cf. Fig. 4A).