The first complete three-dimensional ultrastructural reconstruction of a cyanobacterium was accomplished with high-voltage electron microscopy and computer-aided assembly of serial sections. The precise arrangement of subcellular features within the cell body was very consistent from one cell to another. Specialized inclusion bodies always occupied specific intracellular locations. The photosyn...

As developmental biologists come closer to understanding at the molecular and genetic levels how a zygote becomes an adult, it is easy to forget that the very phenomenon that gives them an occupation remains a vexing problem to evolutionary biologists: why do unicellular stages persist in life histories of multicellular organisms? There are two explanatory hypotheses. One is that a unicellular ...

Tritiated diazepam accumulates mainly in the mitochondria of the unicellular Tetrahymena. This is the case in both a single (the first encounter) and a repeated (one day or a week after the first) administration of the drug. When imprinting of Tetrahymena by diazepam (the first encounter) is followed a week later by the administration of the labelled drug, the membranes of the vesicles, too, sh...