Abstract
The length of immaturity in Paramecium caudatum was investigated counting the fissions exactly in daily isolation culture in depression slides and the following results were confirmed.
(1) The length of immaturity depends upon the times of fissions rather than days when temperature limits the fission rate.
(2) Mitomycin C shortens the length of immaturity about 10 fissions.
(3) The maturity in the clones determined to mating type V appears about 10 fissions earlier than those determined to mating type VI.
