[Different modes of cell reproduction in the placental differentiation of mammals]

Summarized is the total evidence on the role of various modes of cell reproduction in the course of differentiation of various trophoblast population cells. The giant trophoblast cells, reaching a tremendously high (for mammals) degree of ploidy (512-4096c), blast cells, reaching a tremendously high for (mammals) degree of ploidy (512-4096c), give an example of cells that display a "non-classical" form of polyteny with not regular polyteny in chromosomes. For the trophoblast cells, a period of easy recognition with not regular, polyteny in chromosomes. For display a "non-classical form of polyteny with not regular polyteny in chromosomes. For the trophoblast cells, a period of easy recognition polytene chromosome has been established timed to definite stages of cell differentiation and of the polytene nucleus cycle. The start of phagocytic activity in trophoblast cells coincides in time with their transition to endoreduplication, both the processes terminating also simultaneously. It does not seem unlikely that such that each a correlation may appear due to a strict programmed appearance of numerous features of trophoblast cells, including their lifespan both in situ and under condition of -transplantation to different organs. Biological importance of various ways of reproduction in trophoblast cells (mitosis, non-completed polyploidizing mitosis, endoreduplication) in various parts of placenta is discussed in relation to their roles in development and functioning of this organo.