[Some regulatory mechanisms of asexual reproduction in planaria].

The conditions were studied which influenced the reproduction of an asexual race Dugesia tigrina. The decapitation was shown to arrest divisions until the restroration of a new ganglion. The division of intact planarians does not depend on the presence of additional cut head regions and is inhibited in the presence of other intact or decapitated specimens. These data suggest that two antagonistic factors influence the division of planarians: a stimulating factor is related to the activity of the ganglion and is propagated endogenously; an inhibiting factor is localized in the trunk or tail regions. The latter may be secreted outside and influence other specimens.