The effect of conjugation

Abstract

A single individual (ex-conjugant) of Uroleptus mobilis was isolated November 20, 1917. Five lines of the series were maintained by the usual daily isolation culture method used with infusoria. The relative metabolic activity is indicated by the average division rate of all five lines of the series for ten-day unit periods extending throughout the life cycle. Once a week, the excess individuals, after the isolations are made, are placed in larger culture dishes for a conjugation test. Here they multiply by division, until, in a week or ten days, thousands of individuals are present. With increasing scarcity of food they will conjugate, provided the protoplasm is sexually mature. From time to time, ex-conjugants, obtained from such conjugation tests, are isolated to form the beginnings of filial series. These are similarly maintained in daily isolation cultures, five lines to each series, and all fed at the same times and on the same standardized culture medium as the individuals of the parent series. This method furnishes the possibility of comparing the vitality of a filial series with that of the parent series. The protoplasm of 16 such series has been studied, each series represented by five lines; seven series have died and nine are still under observation in different stages of vitality.

The process of parthenogenesis (“endomixis” of Woodruff and Erdmann) occurs in Uroleptus while encysted. These cysts require drying before the individuals will emerge. Parthenogenesis, therefore, is too clearly advertised to be overlooked, and the effects of such asexual reorganization cannot confuse the results obtained by the isolation cultures, for, while parthenogenesis occurs in the conjugation tests, it never has occurred in the isolation cultures.

In these experiments we deal with one protoplasm originally contained in the single-celled ex-conjugant of the A series.