A microscopical study of a marine species of Codosiga James-Clark (Choanofiagellata) with special reference to the ingestion of bacteria

Cells of Codosiga gracilis (Kent) de Saedeleer were grown in culture with two strains of bacteria and observed over a period of almost two years. Throughout the growth cycle, cell form varied with rounded motile individuals predominating during the first three days after subculture and stalked cells predominating in older cultures. Electron microscopy of sections revealed the presence of at least two flagellar bases and an elaborate microtubular system associated with the base of the single emergent flagellum. Capture and ingestion of bacteria has been observed using light microscopy, and electron microscopy of sections has demonstrated the relationship between the engulfing pseudopodium and adjacent collar tentacles.