The idea of mitochondria as captured bacteria traced to Wallin, and she knew it. Chloroplasts as captured bacteria traced to Merezhkowsky, and she knew it. In this 1967 paper, she added something more: another aspect of eukaryotic cells, possibly also originating from endosymbiosis. Her addition comprised three features she saw as related: the flagella of tiny swimming eukaryotes such as Euglena gracilis (on which she had done her dissertation); the cilia, little hairs that project from virtually every eukaryotic cell, including the cells of your body; and the centrioles,
