PHESIDENTIAL ADDRESS. 449 



(7) Amongst minor differences, niycoplasm is characterised by tlie presence of 

 iron in the combined state and possesses a far more complicated structure 

 than amoeboplasm, a peculiarity which enables mycoplasmic cell-elements 

 (chromosomes) to function as the bearers of hereditary qualities. 



The course of the evolution of living beings, according to Mereschkowsky, 

 was as follows. The earliest forms of life were ' Biococci,' minute ultra- 

 microscopic particles of mycoplasm, without organisation, capable of existing at 

 temperatures near boiling-point and in the absence of oxygen, possessing the 

 power of building up proteins and carbohydrates from inorganic materials, and 

 very resistant to strong mineral salts and acids and to various poisons. From 

 the Biococci arose in the first place the Bacteria, which for a time were the 

 unly living inhabitants of the earth. Later, when the temperature of the 

 terrestrial waters had been lowered below 50° C, and contained abundant 

 organic food in the shape of Bacteria, amoeboplasm made its appearance in small 

 masses as non-nucleated Monera which crept in an amoeboid manner on the floor 

 of the ocean and devoured Bacteria. 



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 symbiotic 

 micrococci were scattered in the Moneran body, but later they became concen- 

 trated at one spot, surrounded by a membrane, and gave rise to the cell- 

 nucleus. In this way, by a ' symbiogenesis ' or process of symbiosis between 

 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 producing ferments of the most varied 

 kinds. 



Meanwhile it is supposed that the free Bacteria continued their natural 

 evolution and gave rise to the Cyanophycese, 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 colour, became symbiotic in 

 nucleated cells, for the most part flagellates, in which they established them- 

 selves as the chromatophores or chlorophyll-corpuscles. In this way Meresch- 

 kowsky beUeves the vegetable cell to have come into existence, and the 

 evolution of the Vegetable Kingdom to have been started, as a double process 

 of symbiosis. Those amceboid or flagellated organisms, on the other hand, which 

 formed no symbiosis with Cyanophycese, continued to live as animals and started 

 the evolution of the Animal Kingdom. 



As a logical deduction from this theory of the evolution of living beings, 

 Mereschkowsky classifies organisms generally into three groups or Kingdoms : 

 first the Mycoidea, comprising Bacteria, Cyanophycese, and Fungi, and in which 

 no symbiosis has taken place ; secondly, the Animal Kingdom, in which true 

 cells have arisen by a simple symbiosis of mycoplasm (chromatin) and amoebo- 

 plasm (cytoplasm) ; thirdly, the Vegetable Kingdom, in which true cells have 

 entered upon an additional symbiosis with Cyanophycese, chromatophores or 

 chlorophyll-corpuscles. 



Interesting and suggestive as are the speculations of Mereschkowsky, they 

 are nevertheless open to criticism from many points of view. I will not enter 

 here into criticisms which I regard as beyond my competence. It is for botanists 

 to pronounce upon the notion that Bacteria, Cyanophycese, and Fungi can be 

 classified together as a group distinct from all other living beings ; to decide 

 whether the protoplasm of the Cyanophycese and Fungi can be regarded as 

 consisting of mycoplasm alone, and not of a combination of nuclei and cyto- 

 plasm, such as is found in true cells and represents, according to Mereschkowsky, 

 a symbiosis of mycoplasm and amoeboplasm. I think I am right in saying 

 that botanists are agreed in regarding Fungi as derived from green algse, and as 

 possessing nuclei similar to those of the higher plants. As a zoologist the point 

 that strikes me most is the absence of any evidence that true Monera, organisms 

 consisting of cytoplasm alone, exist or could ever have existed. Mereschkowsky 

 supposes that when the Monera came into being they maintained their existence 

 by feeding upon Bacteria. In order to digest Bacteria, however, the Monera 

 must have been capable of producing ferments, and therefore did not acquire 

 this power only as the result of symbiosis with Bacteria, unless it be assumed 

 J91;j.. . (J (1 



