Summary of the major results.

The effects on receiver populations depend on the number of receiving and/or sender cells in the inner and outer cuvette (the so called units) as well as on the separating material (quartz or glass). In experiment 1a and 2 cell division (growth) was assessed 48 hrs after the mutual exposure of cell populations. In experiment 3 energy uptake (vacuole formation) of cells was assessed 3 hrs after the mutual exposure.*For experiment 1a see also figure 3, tables 2 and 3; for exp. 2 see figure 4 and table 4; for exp. 3 see figure 6 and table 5.**The significance of these effects follows from a contrast analysis, which is described in the text.