Oviduct development inDrosophila : II. Metamorphic events in normal and ovariectomized females.

The course of development of the lateral oviducts ofDrosophila virilis was investigated in normal unoperated animals and subsequent to unilateral and bilateral larval ovariectomy. The development of the epithelial component of the oviducts can be divided into three phases, each characterized by different processes of growth. During the first two days following puparium formation, growth of the oviducts occurs through morphogenesis and mitotic activity. As the cell number increases, all the primordia characteristic of the imaginal reproductive system become recognizable. Early in this phase, a bifurcation of the oviducal rudiment becomes evident, thereby indicating distinct development of the lateral oviduct pair. With the cessation of cellular divisions by about 54 hours after puparium formation, a second phase of growth occurs through alterations in the arrangement of the cells and in their morphology. The third phase begins toward the end of pupal life. It is characterized by cellular enlargement and cytodifferentiation. These processes are not completed at the time of eclosion of the adult females and continue to occur during the first few days of imaginal life. Details of the histogenesis of oviducal epithelium and muscle are described. The course of development of free lateral oviducts obtained after either unilateral or bilateral ovariectomy was found to be indistinguishable from that of normal oviducts up to and even beyond the stage at which ovarian attachment normally occurs. In the latter part of pupal life, a collapsed configuration that may be the result of mechanical factors is observed in the free lateral oviduct. Differentiation of the epithelium and of oviducal muscle, however, proceed normally in such structures, at least until the time of eclosion. No evidence can be offered to support the previously reported view that outgrowth of lateral oviducts is dependent upon an induction by the ovaries.