Stomatogenic Events Accompanying Binary Fission in Blepharisma*

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Abstract
Stomatogenesis was studied in the heterotrich ciliate B. japonicum stained with protargol. During binary fission not only is a new oral apparatus made for the posterior daughter, but the already existing oral apparatus of the parent cell is reorganized, i.e., partially disassembled and then subsequently reassembled to provide a functional feeding apparatus for the anterior daughter cell. These morphogenetic events, requiring 2 1/2-3 h, are complete by the time the anterior and posterior daughters separate. In preparation for division, an oral anlage is formed by the rapid proliferation of kinetosomes along 4-5 stomatogenic kinetics directly subtending the cytostome. This field of randomly oriented kinetosomes ultimately gives rise to the feeding apparatus of the posterior daughter cell. Early in division the oral anlage separates into 2 longitudinal fields of kinetosomes: one destined to give rise to the undulating membrane and the other the adoral zone of membranelles. Shortly after the anlage is established posterior to the cytosome, reorganization of the existing functional mouth is initiated. The morphologic changes associated with this dedifferentiation-redifferentiation sequence lead to the formation of an oral apparatus for the anterior daughter and cannot be distinguished from those characteristically seen during physiologic reorganization.