Elsberg's Plastidules 47 



As long as we are concerned only with the explana- 

 tions of the chemical processes in cell-life, this hypothesis 

 is certainly highly satisfactory. The production of vari- 

 ous compounds, as for example, the red coloring matter 

 of a flower, can be imagined as a function of definite 

 molecules of the protoplasm, more or less in the same 

 manner as the action of enzymes or chemical ferments. 

 Even the secretion of cellulose one might try to explain 

 thus by analogy. As soon, however, as we have to do 

 with morphological processes, this hypothesis fails us en- 

 tirely, because the frequently attempted comparison with 

 the formation of crystals furnishes only a remote simi- 

 larity. The hypothesis is quite useless when applied to' 

 that peculiar attribute of life, growth through assimila- 

 tion. It is obvious that any attempt to explain life-pro- 

 cesses from the properties of chemical molecules must 

 consider this phenomenon first of all. But in the great 

 realm of the lifeless there is no analogy for it. Chemical 

 molecules do not grow in such a way as to separate later 

 into two molecules which are like the original one. They 

 do not assimilate, and in this sense they are not capable 

 of independent multiplication. They do not possess any 

 qualities at all from which one could at present hypotheti- 

 cally explain a growth through assimilation. 



Here lies the great difficulty of the plastidule hy- 

 pothesis. Indeed, Haeckel says, "Besides the general 

 physical properties, which modern physics and chemistry 

 ascribe to the molecules of matter in general, plastidules 

 possess some special attributes which are exclusively 

 their own, and these are, quite generally speaking, the 

 life-attributes which, according to the present concep- 

 tion, distinguish the living from the dead, the organic 

 from the inorganic." But it is easily understood that by 



