The origin of secretory cells inCordylophora caspia during regeneration.

Previous studies withHydra viridis (Rose and Burnett, 1968b, 1970) demonstrated that both zymogen cells and gastrodermal basophilic cells differentiated into mucous cells in regenerating hypostomes. It remained to be demonstrated that interstitial cells are the source of the basophilic cells seen in the regenerating hypostome; that is, did they migrate into the gastrodermis during regeneration and differentiate into mucous cells ?This study was undertaken withCordylophora caspia to demonstrate that interstitial cells do differentiate into secretory mucous cells. This hydroid has a distribution of secretory cells similar to that ofHydra viridis. Furthermore, both the epidermis and gastrodermis can be readily isolated from theCordylophora stolon free from contamination by the other layer. Cordylophora can be cultured in a medium containing labeled cell precursors and afterwards be used to obtain pieces of labeled epldermis. These labeled pieces of epidermis were recombined with unlabeled gastrodermis and the resulting expiant was studied histologically, radioautographically, and with the electron microscope to determine if interstitial cells migrate into the gastrodermis and are the source of any specialized cells in this cell layer.The results of this experiment clearly demonstrated that interstitial cells do migrate into the gastrodermis and differentiate into the hypostomal mucous cells and zymogenic cells of that layer.