202 Simple Forms of Life. 



It is no part of the intention of these papers to act as a sub- 

 stitute for works of microscopic natural history, to which the 

 reader must be referred when he wishes to discover the name 

 of any particular object, but we shall make some general 

 remarks that may facilitate his search. A simply organized 

 body is likely to be a plant when it contains a substance like 

 chlorophyll, or green sap, or when it is brown, or red, of the 

 tints well known in leaves. Of course the distinction must be 

 made between the chlorophyll. matter properly belonging to an 

 organism, and that which may have been swallowed by it. The 

 possession of cilia or whips does not decide animality or vege- 

 tality, but moveable styles, hooks, etc., characterize some of the 

 higher animalcules. Red spots looking like eyes are no evidence 

 of animality. The euglense possess them, and they can only be 

 distinguished from true red eyes, as may exist in rotifers, by 

 the use of high powers, which shows whether an optical 

 structure really exists. 



In studying simple vegetable forms, no object is more 

 accessible than the green slimy stuff that grows on damp 

 stones. A little piece should be scraped off and placed in a 

 drop of water, on a slide, covered with thin glass and gently 

 pressed. It is then ready for view, and is seen to be com- 

 posed of oval or rounded patches of green matter, enclosed 

 in a gelatinous envelope. The multiplication of these patches 

 takes place by division of the cells. First the cell contents 

 take an hour-glass form, then a constriction appears, finally 

 a division, each half finishing itself off, secreting more of the 

 gelatinous casing, and being ready to split again as before. 

 Sometimes two cells will join and fuse together, with a certain 

 mingling of contents. This is called conjugation, and from it 

 a spore results, and that in its turn gives rise to a new indi- 

 vidual, which by the mode of fission just described soon pro- 

 duces a fresh generation. In damp weather this plant, the 

 Palmoglcea macrocccca, and many other objects more or less 

 resembling it, multiply with great rapidity by the method of 

 division ; a little more warmth and dryness promotes the con- 

 jugation, and checks the fission. This is somewhat analogous 

 to what takes place with the aphides, or plant lice, which mul- 

 tiply by an internal method analogous to vegetable budding, 

 while the circumstances favour their rapid growth, and start a 

 fresh generation by the united action of males and females, 

 when the means of subsistence, and the temperature, are less 

 plentiful and propitious. 



A great many simple vegetables -exist during a portion of 

 their lives, or in one of their stages, in a motile form, and 

 many little objects taken by early observers for animalcules 

 are plants in this condition. This is the case with the euglense, 



