LIFE 



ming in water. Other species secrete homogeneous jelly- 

 like envelopes — a purely chemical process. In some of 

 fhe chromacea the blue-green coloring matter (^phyocyan) 

 is stored in the surface-layer of the particle of plasm, 

 while the inner part is colorless — a sort of "central 

 body." However, the latter is by no means a real, 

 chemically and morphologically distinct, nucleus. Such 

 a thing is completely lacking. The whole life of these 

 simple, motionless globules of plasm is confined to their 

 metabolism (or plasmodomism, chapter x.) and the re- 

 sulting growth. When the latter passes a certain stage, 

 the homogeneous globule splits into two halves (like a 

 drop of quicksilver when it falls). This simplest form of 

 reproduction is shared by the chromacea (and the 

 cognate bacteria) with the chromatella or chromato- 

 phora, the green particles of chlorophyll inside ordinary 

 plant-cells ; but these are only parts of a cell. Hence no 

 unprejudiced observer can compare these unnucleated 

 and independent granules of plasm with real (nucleated) 

 cells, but must conceive them rather as cytodes. These 

 anatomic and physiological facts may easily be observed 

 in the chromacea, which are found everywhere. The 

 organism of the simplest chromacea is really nothing 

 more than a stiuctureless globular particle of plasm; 

 we cannot discover in them any composition of dif- 

 ferent organs (or organella) for definite vital functions. 

 Such a composition or organization would have no 

 meaning in this case, since the sole vital purpose of 

 these plasma-particles is self-maintenance. This is 

 attained in the simplest fashion for the individual 

 by metabolism; for the species it is effected by self- 

 cleavage, the simplest conceivable form of reproduc- 

 tion. 



Modern histologists have discovered a very intricate 

 and delicate structure in many of the higher unicellular 

 protists and in many of the tissue-cells of the higher 

 ^ 33 



