Vol. 7, 1921 
ZOOLOGY: L. L. WOODRUFF 
43 
culture's first five years of life, during which over 3029 generations 
were attained, the writer stated that "the organisms of the present 
generation are in as normal morphological and physiological condition 
as the original 'wild' individual isolated to initiate the culture. 
This study has indicated that, under favorable environmental conditions, 
the protoplasm of the cell originally isolated possessed (at least) the 
potentiality to produce similar cells to the number represented by 2 
raised to the 3,029th power, or a volume of protoplasm not less than 
10 1000 times the volume of the Earth. I believe this result indicates 
beyond question that the protoplasm of a single cell may be self-sufficient 
to reproduce itself indefinitely, under favorable environmental conditions, 
without recourse to conjugation " 
As a matter of fact organisms taken from this culture of Paramecium 
have shown but little tendency to conjugate. From time to time experi- 
ments to induce conjugation have been carried out in mass cultures 
started from the pedigree lines. The first successful experiment occurred 
in December, 1913, at about the 4100th generation. 2 The next epidemic 
of conjugation in mass culture occurred June, 1920. 
Careful studies of the rate of division of sub-lines derived from the 
main lines and bred under the most constant environmental conditions 
revealed the fact that there are inherent, normal, minor, periodic rises 
and falls of the fission rate due to some unknown factor in cell phenomena. 
These were termed Rhythms. 3 In a search for the underlying factors of 
rhythms a complicated internal nuclear reorganization process was dis- 
covered and named Endomixis. 4 This process involves the periodic 
formation of a complete new nuclear apparatus by a definite sequence of 
normal morphological changes which simulate those occurring in con- 
jugation. Endomixis, in essence, consists of a gradual disintegration and 
absorption of the macronucleus in the cytoplasm. Simultaneously a 
multiplication of the micronuclei is in progress. Certain of the resulting 
micronuclei degenerate while the remaining one or two form the new 
macronuclear and micronuclear apparatus of the cell. This results in the 
YEAR 
GENERATIONS 
DAILY AVERAGE 
DIVISION RATE 
1 
2 
3 
4 
5 
6 
7 
8 
452 
690 
613 
612 
662 
692 
671 
679 
1.24 
1.89 
1.68 
1.67 
1.81 
1.89 
1.84 
1.86 
Average for 8 yrs. 
634 
1.74 
