350 THE BACTERIOPHAGE AND ITS BEHAVIOR 



property the elementary particle is a colloidal polarized "micella," and 

 by virtue of this fact its mass is limited by a purely physical phenome- 

 non, as has been very clearly stated by Perrin. "If," he says, "one 

 admits that the charges of the particles are due to the H+ and the 0H~ 

 ions which are disseminated throughout the liquid and which become 

 fixed to the particle, it is obvious that when the particle has attained a 

 certain size, and provided the number of free ions is suffi.ciently great 

 to afford more available for fixation, this increase in size will inherently 

 be a cause of rupture, leading to a division into two parts." This 

 physical phenomenon applies without discrimination to the cells of the 

 body, to the bacterium, and to the infra visible virus. 



The faculty of multiplication consequent upon assimilation in a ho- 

 mologous or heterologous medium is not, then, a characteristic of life. 

 That all living beings possess it is true, but this is solely because they 

 possess the power of assimilation. The bacteriophage corpuscle is 

 endowed with this faculty, and from it all of the phenomena of bacteri- 

 ophagy are derived. 



7. VARIABILITY OF THE BACTERIOPHAGE 



The power of adaptation, which is an attribute of all living beings, 

 entails, naturally, a lack of fixity in the characters of a hving being; it 

 demands that they be dependent upon their environment. The same 

 being placed under different conditions exhibits different characters. 



But adaptation is accompanied by another phenomenon. Living 

 matter, protoplasm, retains the impression of the reaction effected, an 

 imprint whose mark in the substance is engraved the more deeply as the 

 reaction is the more intense. Obviously, it is unnecessary to attach to 

 the word "impression" any psychic meaning. As used here it implies 

 simply that living matter which has once reacted to a given stimulus 

 reacts again more quickly, and in general, more intensely when subjected 

 to a second stimulus of the same nature as the first. That the reaction 

 of living matter is specific, we have said. The "recollection" is like- 

 wise specific, for it modifies in no way the response to a different 

 excitation. 



This "reactional memory" is transmitted hereditarily,* but if a_stimu- 



* Here, of course, we are not considering the case, still very obscure, of the 

 transmission of characters to descendents through the intermediary of gametes. 

 The only transmission of characters with which we are concerned here is that 

 which takes place when a cell becomes two cells through division. Here, the 

 transmission of acquired characters is beyond doubt. All immunity demonstrates 

 this, as do the facts of all types of adaptation which can be experimentally effected 

 with bacteria. 



