294 Ewartj The Relations of Chloroplastid and Cytoplasma. 



In certain cases Kny and Kolkwitz state that chloro- 

 phyllous cells killed by electricity*), Chloroform, or nitric acid, 

 continue apparently for a considerable time to assimilate and 

 evolve oxygen. This is hardly surprising, considering that they 

 used impure cultures and unringed preparations. Motile anaerobie 

 bacteria will shew an attraction to, and movement in the neigh- 

 bourhood of, dying or dead cells for a day or more, in the 

 apparent absence of all external supplies of oxygen. The same 

 is the case with Bacterium Termo, if a slight amount of oxygen 

 be allowed to diffuse throughout the fluid in which it lies. The 

 attraction is due to the nutritious substances evolved from the 

 dying cell, and unless a definite attracting cause be present, the 

 Bacteria always distribute themselves evenly throughout the 

 enclosed fluid. 



Many more or less anaerobie forms when placed in a closed 

 ringed preparation in water, though at first immotile or nearly 

 so, may begin to shew in a short time more or less active move- 

 ment, i. e., apparently they are immotile when the oxygen partial 

 pressure is high, motile only when it is low. 



It is important to remember that the sensitivity of Bacterium 

 termo is not always the same. In water it ceases to move when 

 the partial pressure of the enclosed oxygen reaches a certain 

 inhibitory limit. In nutrient Solutions the movement continues for 

 a longer time and until a lower partial pressure is reached. On 

 the other band, Bacterium Termo, fresh from agar cultures, requires 

 a higher partial pressure of oxygen to permit of movement, than 

 when it has been kept in pure water for some time. Starvation 

 increases the sensitivity of the Bacteria to oxygen. A slight 

 amount of CO2 increases, a large amount depresses the sensitivity 

 of the Bacteria to oxygen and their rapidity of movement. In 

 addition, if a cell is only thinly ringed with vaseline (this was 

 not even considered necessary by Kny and Kolkwitz) a slight 

 amount of oxygen, sufficient to permit of the movement of less 

 strongly aerobic forms than Bacterium Termo, and to allow slow 

 rotation to continue in enclosed end-cells of Ohara kept in 

 darkness, diffuses in. In all such experiments the most careful 

 ringing in necessary (p. 420. A^). 



Kny and K o 1 k w i t z state, however, that the evolution of 

 oxygen seen by them, tooke place only in light and ceased in 



*) In the case of Spirogyra filaments, killed by the passage of elec- 

 tric ciirrents, one possibility must not be ignored, viz. that the filament may 

 be converted into a secondary battery, the dead cells near the positive elec- 

 trode being charged with electrolytic oxygen, which may in part slowly be 

 evolved, for a time, after the current haa ceased. In the living cell this 

 oxygen combines with the plasma. Hence, asseems to be schewn by experi- 

 ments at present in progress, the cells near the positive electrode are most 

 markedly affected. Also, using weak currents enduring for a considerable 

 time, the ectoplasmic layer in Nitella may be killed and assimilation cease, 

 although the endoplasmic layer is still shewing slow rotation. 



