GREAT STEPS IN ORGANIC EVOLUTION 851 



chromatin corresponds to the Biococci (mycoplasm), and the 

 cytoplasm to Monera (amoeboplasm). So the somewhat luxuriant 

 speculation continues! 



But from simple flagellate or amoeboid organisms there was 

 evolved the Vegetable Kingdom as well, apart from the Bacteria, 

 Cyanophycese, and Fungi. For Mereschkowsky supposed that 

 certain Cyanophycese entered into partnership with the true cells 

 already accounted for, and were eventually represented by the 

 chromatophores or chlorophyll-corpuscles of green plant cells. 

 Thus green plants would arise by a double symbiosis. Further 

 speculation is aroused by the comparatively recent discovery of 

 filter-passing organisms. 



BACTERIAL FORM AND LIFE .—Nothing is more characteristic 

 of our habits of thinking and teaching in biology than our customary 

 start with the "Proteus animalcule" of old naturalists, the common 

 Amoeba, as one of the simplest and most elemental forms of life 

 within easy observation ; so this affords not only a convenient start 

 for teaching, but interest ever yielding fresh ideas and results. 

 These we carry onwards from this simple life-form and its life-cycle 

 to the multitudinous variety of protozoan and protophytic forms. 

 From these, we consider our best way of approach to the "higher" 

 — ^because multicellular and integrated — Metazoa, and find the 

 sponges easiest to begin with, albeit with their own complexities 

 beyond the unknown simpler predecessors we may try to imagine. 

 So, too, the botanical teacher starts with his simplest unicellular 

 Algae, and goes onwards. Since among the simplest Protozoa and 

 Protophytes there are forms which can hardly be considered as yet 

 distinctly animal or vegetal in character, there is something to be 

 said for Haeckel's union of such forms into a group below Protozoa 

 and Protophytes, as Protista: but the present point is, that all 

 these ranges of organic life are unified within the great generalisation 

 of the cell- theory ; since our biological observations and interpreta- 

 tions have essentially arisen within its limits. 



The comparatively recent yet now extensive field of Bacteriology, 

 however, lies very largely outside and beneath that of ordinary 

 zoological and even botanical thought, though every botanist may 

 teach its first elements. Its medical and even its economic interests 

 have each evoked their own specialists; and it is interesting that 

 these new groups of experts differ not a little from us older natural- 

 ists, and even from each other, in their ways of work and thought, 

 evolving not only techniques of their own, but theories and specula- 

 tions too. And though some protistologists have been struck by the 

 resemblance of flagellate bacilli to certain very simple flageUate 

 infusorians, and mycologists have often endeavoured to connect 

 bacteria with fungus moulds, whether as degenerate forms or 



