Elimination of zymogen cells and their derivates in Hydra.

Budles and one-budded hydras were exposed to action of antimite (N-methyl-bis-chlorethylamine hydrochloride, Pliva, Zagreb) in 7 mg/150, 7 mg/200 and 7 mg/250 ml concentrations. All these concentrations caused exterior morphological and cytological changes of the hydra body. In the ectodermal layer interstitial cells gradually disappeared, and then followed enidoblasts and enids. The discussion deals with interstitial cells in a normal untreated animal and possible differentiation of these cells in enidoblasts and enids after the action of antimite. Antimite prevents mitosis, but it does not stop differentiation of some of the cells into other cell types. In the gastrodermal layer the greatest changes which are caused by this cytostatic can be seen on zymogen cells. Their shape, cell structure and position in the gastroderm is changed. The results show that zymogen cells after the antimite action have a limited ability of dedifferentiation into gastrodermal interstitial cells, and that their ability to differentiate into mucous cells lingers a longer time. This depends upon their age. Only the hydras which were acted upon by such a dose of antimite that does not prevent division at last some of the zymogen cells can survive and wholly continue their development.