Growth, Metabolism, and Structure

Abstract

Upon reaching a certain size and maturity, Euglena divides in two; sexual reproduction is unknown. Nuclear and cytoplasmic division takes place. Division necessarily is complicated; not only the nucleus but also the organelles, chloroplasts, eyespot, and flagellum are independently self-reproducing, or at least do not lose their identity during division. Leedale (1958), who studied nuclear division in 32 species of the Euglenaceae from 13 genera, observed true mitosis, but the mitosis differed from the “classical” form in that the endosome of the nucleus persists throughout mitosis, dividing as a structure distinct from the chromosome. He also noted that E. gracilis had 45 chromosomes and that mitosis lasted from 2 to 5 hours, of which the anaphase took from 35 to 86 minutes. This rate is slow when compared with that of other organisms and tissue cells, in which anaphase takes from 1 to 20 minutes.