Cix. the Rate of Reproduction in Artificial Culture of Colpidium

IN a previous paper [Cutler and Crump, 1923] an account of experiments on mass cultures of Colpidium colpoda was given; the present communication deals with similar experiments carried out on cultures containing one or more cells isolated into one cubic centimetre or less of culture solution. The objects of these experiments have been to discover whether the results obtained from cultures containing few organisms in small quantities of fluid are comparable with those in which numerous animals are inoculated into comparatively large amounts of liquid, 10 cc. or more. Also there have appeared a series of papers by Robertson [1921, 1922], describing new and interesting phenomena -allelocatalysis, etc.-in cultures of a ciliate Enchelys farcinem. These seemed to be of so fundamental a character that it was felt desirable to test whether they obtained with other species of ciliates.