THE EVOLUTION OF THE CELL 



31 



The next step in evolution is supposed to have been 

 that, in some cases, micrococci ingested by the Monera 

 resisted digestion by them and were enabled to maintain a 

 symbiotic existence in the amoeboplasm. At first the sym- 

 biotic micrococci were scattered in the Moneran body, but 

 later they became concentrated at one spot, surrounded 

 by a membrane, and gave rise to the cell-nucleus. In this 

 way, by a ' ' symbiogenesis " or process of symbiosis be- 

 tween two distinct types of organisms, Mereschkowsky 

 believes the nucleated cell to have arisen, an immense step 

 forward in evolution, since the locomotor powers of the 

 simple and delicate Monera were now supplemented by 

 the great capability possessed by the Bacteria of produc- 

 ing ferments of the most varied kinds. 



Meanwhile it is supposed that the free Bacteria con- 

 tinued their natural evolution and gave rise to the Cyano- 

 phyceae, and to the whole group of Fungi. The plant-cell 

 came into existence by a further process of symbiogenesis, 

 in that some of the Cyanophycese, red, brown or green in 

 color, became symbiotic in nucleated cells, for the most 

 part flagellates, in which they established themselves as 

 the chromatophores or chlorophyll-corpuscles. In this 

 way Mereschkowsky believes the vegetable cell to have 

 come into existence, and the evolution of the Vegetable 

 Kingdom to have been started, as a double process of sym- 

 biosis. Those amoeboid or flagellated organisms, on the 

 other hand, which formed no symbiosis with Cyanophy- 

 cea?, continued to live as animals and started the evolu- 

 tion of the Animal Kingdom. 



As a logical deduction from this theory of the evolution 

 of living beings, Mereschkowsky classifies organisms gen- 

 erally into three groups or Kingdoms : first the Mycoidea, 

 comprising Bacteria, Cyanophycea?, and Fungi, and in 

 which no symbiosis has taken place ; secondly, the Animal 

 Kingdom, in which true cells have arisen by a simple sym- 

 biosis of mycoplasm (chromatin) and amoeboplasm (cyto- 

 plasm) ; thirdly, the Vegetable Kingdom, in which true 



