152 



THE BEGINNINGS OF LIFE. 



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acknowledged that the cell may or may not be enclosed 

 by a membrane or cell-wall. For the structureless mass 

 of protoplasm — the mere bit of plasma, or living matter 



in which no inner differentiation has yet taken place 

 we cannot do better than adopt Haeckel's^ term '•^lastUe' 

 The plastide^ like the cell, may vary much in size: it^ 

 also, may be either naked or bounded by a membrane. 



The old doctrine as to the fundamental properties of 

 the ^ ceir as a vital unit, did well enough in those days 

 when the lowest known living things — the lowest plants 

 and the lowest animals — were thought to be ^unicellular 



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Fig. 5. 



'Unicellular Organisms.' 



a, b, c. Three of the higher Amoebae, f. One of the most minute and 



a. Nuclearia simplex, 



b. Amceba Limax, 



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c. Amceba guttula. 

 d and e. Gregarina Siptinculi, 



simple of the unicellular Al- 

 gae — Hematococcus ceruginosus. 



g. The *red snow' Alga— Pro/o- 



coccus nivalis. 



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Journal of Microsc. Science/ 1869, vol. ix. p. 332. 



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