Abstract
Recently I have shown that if a small piece of the plasmodium of Physarum polycephalum be forced through a gauze with sufficiently small pores (less than 0.25 mm. in diameter) subsequent growth of this material does not occur, whereas if the pores are larger, growth takes place when the material is put on the culture medium. The experiments were repeated and confirmed for P. rigidum. During the present summer I have confirmed in the main the previous results and have extended the experiments to follow the respiratory changes in P. polycephalum. As gauze sieves I have used Latimer's “Old Anchor Brand” calibrated bolting cloth Nos. 00, 4, 6, 8, 10, 14, and 21 which have average pore sizes of 0.75, 0.32, 0.24, 0.20, 0.155, 0.10 and 0.07 respectively. When strained through the last 3 the plasmodium gave no growth; when the 0.20 sieve was used the strained plasmodium sometimes grew, sometimes not; with sieves of larger pores active plasmodium when forced through, grew on the culture medium. On the other hand, Plasmodium if allowed to grow in gauze bags, passed through all the sieves as well as hard paper filters onto the culture medium. In 5 hours plasmodium made its way through hard filter S. & S. No. 575A which has an average pore size of 1 μ. These facts confirm the conclusions previously stated that essential to the life of the Plasmodium are filaments or fibrils which may be 0.20 mm. in length but in diameter are below visibility with the microscope.
Since viability is so conspicuously reduced by comminuting the plasmodium it seemed important to determine whether metabolism as indicated by consumption of oxygen might not also be modified in this way.
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