EGF and cyst: Based on the mutant phenotypes caused by the loss, reduction, and increase of EGF signaling, we propose that EGF signaling between germline and cyst cells increases as the cysts develop and that different doses of EGF signaling, in turn, induce distinct responses in the cyst cells: germline enclosure, the production of return signals that allow for the germline cells to progress through the early steps of development, the spermatogonia TA-divisions, and the production of return signals that promote terminal differentiation of the cysts (Figure 7).