Parabiotic development of fused eggs from the Hymenopteron, Pimpla turionellae, and of eggs injected with energids.

Explanted oocytes and eggs of different developmental stages from the Hymenopteron Pimpla were fused in pairs as "parabiotic tandems". Interactions within the tandem were analysed by time lapse films. Except for the exchange of nuclei, no joint development was observed, and each partner followed its own time pattern. The rapid cell cycles of the cleavage energids switched over to longer cycles according to the local developmental stage of the different egg regions, although all of the nuclei were still contained in a single plasmodium. In a second experimental series, nuclei in newly deposited eggs were X-rayed and replaced by cleavage energids from later stages injected into the wrong (=posterior) egg pole. Even injected blastoderm nuclei immediately took up mitotic activities and underwent rapid cell cycles characteristic of early cleavage. Normal embryos could be formed, although the nuclei had populated the egg in a reverse direction.