It is supposed that the development and aging of multicellular animals and humans are controlled by a special form of the clock mechanism - a chronograph. The development of animals and their aging are interconnected by the program of the species lifespan that has been selected in the evolution of each species to fit the resources of its ecological niche. The theory is based on the idea about a controlled loss by the neurons in the brain of hypothetical organelles - chronomeres that represent themselves small DNA molecules, which are amplificates of the segments of chromosomal DNA. A regular mode of the process of chronomere losses by neurons is provided by a pacemaker localized in the pineal gland and activated at least once per lunar month. Neurons, consecutively losing their chronomeres, are organized in the brain in the temporal relay race. Analogues of chronomeres, namely printomeres, are supposed to exist in dividing non-neuronal cells. Printomeres are not involved in a performance of temporal function, instead they are responsible for the maintenance in dividing cells of their memory about the state of differentiation. A critical shortening or loss of a printomere in a dividing cell leads to a cellular senescence, whereas telomere shortening is a bystander of this process. Thus, aging of a multicellular organism is associated with the loss of chronomeres, whereas senescence of dividing cells is associated with the loss of regulatory RNAs encoded by printomeres. If the cells that have lost their printomeres are environmentally forced to divide, they can transform into cancer cells.