Inheritance of an abnormality of form in Paramecium aurelia.

Abstract

Previous studies of abnormality of form arising from unknown causes in laboratory cultures of Paramecium have tended to show that such abnormality is not inherited, i. e., at the time of fission only one daughter cell receives the abnormality. Thus, Jennings found, in a Paramecium which developed a spine, that only one of the daughter cells received this modification, and that animals with a truncated anterior end transmitted the truncated condition to only one of the progeny. He also found that the truncated condition was lost after a few divisions, and all of the descendants became apparently normal. Stocking confirms the observations of Jennings in regard to the non-inheritance of abnormality of form. On February 23rd, 1924, the author found, in a laboratory culture of Paramecium aurelia, a number of peculiarly truncated specimens. The truncation was so pronounced that the animals were almost exactly one half the length of a normal Paramecium, and it was only after careful study that it could be identified as belonging to this genus. One hundred and thirty of these truncated individuals were isolated during the next three weeks and pedigree cultures of the progeny were kept for varying lengths of time. The culture medium consisted of timothy hay and whole wheat boiled for five minutes in spring or pond water. Standard quantities of these substances were used in making up each lot of culture medium.