[Recapitulatory significance of coeloblastulas]

The problem is discussed whether in Metasoa evolution there was a blastea stage, or else they were of parenchymal structure from the very beginning. The author favours the colonal theory in Metasoa origin and, as their progressive form, he considers spherical colonies where the cells are not united by intracellular substance but have immediate contact with each other. There are two ways of flagellar cells union: by their lateral surfaces or by basal ends. With the first way of union, a rather large colony acquires inevitably the form of blastea. With the second way of union, the number of cells increases, the colony becomes either a homogenous parenchimella or a blastea. The possibility of both ways of evolutionary development were studied experimentally. The results of artificial mutant selection of zootrophic colonial Euglena, Anthophysa vegetans are represented. The author comes to the following conclusions from the results obtained: 1. In Metosoa phylogenesis a blastea-like stage should be present. 2. Recapitulatory significance of the coeloblastulas is evident.