| Abstract: | Rule I: The more advanced in its primary evolution the life cycle of a cestode is, the greater is the participation of the animal component of the ecosystem in it. The direct influence of the non-living component of the ecosystem on the course of the cycle is one and the same with both the primarily evolved 2-host and 3-host life cycles within the separate orders. Rule II: In the secondarily evolved life cycles of cestodes, when compared with their initial life cycles, the following things are observed: a) either a decrease of both the participation of the animal component of the ecosystem in the life cycle and the direct influence of the non-living component of the ecosystem on the course of the cycle; b) or a decrease only of the participation of the animal component of the ecosystem in the life cycle, without any change in the direct influence of the non-living component of the ecosystem on the course of the cycle; c) or, quite rarely, a decrease only of the direct influence of the non-living component of the ecosystem on the course of the life cycle, without any change in the participation of the animal component of the ecosystem in the life cycle. |
