Growth of larval salivary gland nuclei of drosophila melanogaster in the adult abdomen.

1. Anterior halves of 6-hour-old embryos, in which the primordia of the salivary glands are not yet visibly segregated, have been transplanted into the abdomen of adult females. 2. Normal larval salivary glands differentiate in the adult hemolymph and attain the maximal degree of nuclear size due to polytenisation. 3. In the adult hemolymph, a culture period of 14 days is needed for full development whereas the same end-size is reachedin situ after 4 days. 4. The retardation in growth rate is accompanied by a reduction in cell numbers. 5. It is concluded that the adult hemolymph can provide all factors needed for the entire development of larval salivary glands. 6. The difference between the adult medium and the normal larval milieu which promotes a more rapid development might be only of a quantitative nature. Tentatively, we consider differences in hormonal concentrations.