Fig. 7. Heteroaggregates slowly develop to ecto-/endodermal chimeric polyps. (A—E) H. vulgaris/H. oligactis heteroaggregates 10h, 24h, 7 days, 21 days and 28 days after reaggregation, respectively. H. vulgaris cells are stained with species-specific antiserum visualized with FITC-labelled secondary antibody (green). Unlabelled cells of H. oligactis, couterstained with Toluidine Blue, appear red. (F) Histogram indicating the number of head structures per aggregate (numbers in columns) on day 7 after reaggregation. o/o and v/v, control homoaggregates from H. oligactis or H. vulgaris alone, respectively. v/o, heteroaggregates. (G—I) Interstitial cell differentiation products such as nematocytes are not eliminated in heterografts. Shown is the portion of a tentacle of a heterograft (3 days old) stained with an antiserum specific for H. vulgaris cells. One H. oligactis nematocyte (arrowhead) is embedded next to several H. vulgaris nematocytes (arrows).