[Experimental investigations on the postembryonic differentiation and the regulatory capacities of the male genital imaginal "Anlagen" inLymantria dispar L. (Lepidoptera) : II. Capacities of differentiation and regulation in the Herold's organ].

1. In the first part of the paper the potentiality of autonomous differentiation in the Herold's organ ofLymantria dispar is investigated. a) The development of the implanted Herold's organ is observed in a host; after molting of the imago, the implanted genitale is removed from the body cavity and analyzed. Aedoeagus and anellus are quite normally formed. Two lateral, inverted chitin vesicles are found to be identical with the valvae. All differentiations observed within the complex are homologous with parts derived from the Herold's organ. b) Transplantation experiments show the necessity of the exact position (9th abdominal segment, ventromedian) for the evagination and typical differentiation of the valvae-"Anlagen". This means that the epithelial translocations at the posterior end of the larva during the metamorphosis are essentially engaged in the displacement of the valvae-lobes to the body surface and for their normal development. 2. In the second part of the paper regulation capacity and state of determination of the Herold's organ in the last larval stage is examined. a) Partial and even complete duplication of the aedoeagus is observed after halving the Herold's organ but leaving the epidermal connections of both halves. If-after halving the Herold's organ-the epidermal connection of one half only is removed, both halves show separately the formation of complete genitale. The halfwith epidermal connection is able to develop as an intact Herold's organ, the halfwithout epidermal connection is able to develop as one whole Herold's organ after implantation. In some of the cases regeneration of the removed part does-for unknown reasons-not occur. b) After implantation of a dissected Herold's organ, three classes of results are observed: I. both halves form separately a regenerated, complete genitale, II. only one half regenerates, III. none of the halves regenerate. The regeneration of the removed part occurs during the last larval stage before the onset of the prepupal phase. c) The state of determination of the Herold's organ after subdivision of the primary lobes into the aedoeagus-lobe and the valvae-lobe is analyzed by means of implantation of portions of the Herold's organ. Aedoeagus- and valvae-lobes are irreversibly determined according to their position in the "Anlagenfeld". Regulatory processes are possible only within consistent parts of the "Anlagenfeld".