Allelocatalytic Effect in Cultures of Colpidium in Hay-Infusion and in Synthetic Media

Cutler and Crump have described experiments in which from one to four individuals of Colpidium colpoda were isolated into varying volumes of a synthetic culture medium. Previous experiments by the author [1921, 2] had shown that when two individuals of another ciliate infusorian (Enchelys) are isolated together into a definite small volume of culture medium, the reproductive rate of both individuals is enhanced so that not merely twice, but from four to sixteen times as many individuals may be produced in 24 or 48 hours as in a culture of the same volume into which only a single individual was originally introduced. It was shown that the effect was not due to conjugation, because conj ugation did not occur under the conditions which prevailed in these experiments, while if it had occurred, the result, as Jennings has shown [1913], would have been the opposite of the effect which was observed. This mutual acceleration of reproductive rate by contiguous organisms was termed allelocatalytic effect [1922], and from the autocatalysis which is known to occur during the growth of all organisms, it was inferred that this effect is common to all cells which live in proximity to one another in a limited volume of nutrient medium [1923].