252 



life they have a great affinity for pigments. I venture to think that the loss of the 

 above properties when based, as is supposed, on the becoming inactive or on the de- 

 struction of the more sensitive heredity units or enzymes, can quite well go side by 

 side with the continued activity of another part of the protoplasm, so that then it 

 cannot be said that the cell is dead in the same sense as when all its functions are 

 destroyed. The importance of this view is obvious if we bear in mind that the theory 

 of the units of heredity consists in the very supposition that from their combination 

 energies and activities may arise strange to the units separately. The demonstration 

 of the properties to be ascribed to special factors and of those due to the co-operation 

 of two or more factors is the chief subject of the heredity researches of to-day and 

 the difficulties met with are well known. That the enzyme theory will here be useful 

 is obvious. 



About irritability I need not be long here, as for the lower immotile microbes this 

 conception is only then based on observable facts if we think it conciding with the 

 power of metabolism and of reproduction. 



In this connection I call to mind that the peculiarity of actions caused by stimuli, 

 consists in their showing an optimum for certain intensities of these stimuli, which is 

 also the chief character of enzyme action. So the influence of temperature and of 

 different concentrations of poisons on the process of cell division and on that of amy- 

 lolysis by diastase is analogous, and this is of course one of the best evidences for the 

 correctness of the enzyme theory. 



Phosphorescence considered as bound to protoplasm. 

 Combination of the two views. 



That the function of phosphorescence of the luminous bacteria is bound to the 

 living protoplasm is supported by the following facts. 



Anaesthetics, such as chloroform and aether, stop the light production almost 

 completely, while after vaporisation of these substances it sets in anew only slightly 

 diminished. A short heating of temperatures near 40 to 45 C. of Ph. splendidum 

 and of 30 to 35 C. of Ph. phosphoreum, with subsequent cooling, has the same effect. 

 By the action of acids and alcalies the phosphorescence disappears and returns after 

 neutralisation. A strong salt concentration darkens, after dilution the light is com- 

 pletely restored. Diminution of luminosity in these cases is caused by the dying of 

 part of the germs. The phosphorescence of very active broth cultures, kept at rest for 

 some time, undergoes a sudden and remarkable enhancement in its intensity by 

 mechanical stimuli, such as shaking. The thus produced light reminds of the behaviour 

 of higher luminous animals, possessing a nervous system, which by contact, or other 

 mechanical stimuli, suddenly react with light production. 



All these facts induced me already long ago *) to call the bearer of the phos- 

 phorescence photoplasm and its elementary units photophores. Also for the 

 Flagellate Noctiluca miliaris de Quatrefages has demonstrated that the light 

 issues from the protoplasmic threads that run from the nucleus to the cell-wall which, 

 when seen under the microscope, presents a large number of minute light centres, 



') De Ingenieur, 150 Jaarg. pag. 53, 27 Januari 1900. 



