1. The localization of alkaline phosphatase during the post-embryonic development of Drosophila melanogaster has been described.
2. In the larvae, nuclear phosphatase is always demonstrable, but cytoplasmic phosphatase shows a more restricted distribution. Salivary glands, mid-gut, Malpighian tubes, and pericardial cells are richest in cytoplasmic phosphatase.
3. The larva prior to puparium formation is characterized by a decrease of alkaline phosphatase in the internal organs with a simultaneous increase in the hypodermis.
4. The phosphatase data support the view that the prepupa is actually an intrapuparial larval instar.
5. Pupation is accompanied, by a very noticeable increase of alkaline phosphatase which is mainly confined to the cytoplasm. The high enzyme activity is maintained for the first day and a half after head eversion: there is a subsequent decline until at the time of emergence most organs are inactive. However, certain organs retain their alkaline phosphatase activity.
6. As in embryogenesis, alkaline phosphatase seems to be more concerned with histo-differentiation than with chemo-differentiation.
7. Alkaline phosphatase (and also acid phosphatase) actively participates in the process of histolysis or cellular degeneration.
8. The alkaline phosphatase activity of the pericardial cells, together with other morphological evidence, indicates that these cells are endocrine organs which play important roles in Drosophila metamorphosis.
9. Cytochemical evidence suggests that alkaline phosphatase in Drosophila is probably playing a part in the carriage of organic substances across the membrane barrier.
Relation of Thyroxine Secretion Rate to Serum Alkaline Phosphatase Activity in Growing Japanese Quail Maintained at Different Temperatures