CHAPTER IV 



THE ORGANIZATION OF THE PROTOZOA (Continued) 

 THE PROTOPLASMIC BODY 



THE substance composing the bodies of Protozoa was termed 

 originally sarcode by Dujardin ; but after it had been shown to be 

 identical in nature with the living substance of the cells of animals 

 and plants, the same term was employed universally for both, and 

 the word protoplasm, coined by von Mohl to designate the living 

 substance of plant-cells, supplanted the older term sarcode, which 

 has now quite dropped out of current use. 



It would be impossible within the limits of the present work to 

 discuss in detail the various theories that have been put forward 

 with regard to the nature and constitution of protoplasm ; they 

 can only be summarized in brief outline here. Protoplasm, when 

 seen under the microscope with powers of moderate strength, 

 presents itself as a viscid, semi-fluid substance, sometimes clear and 

 hyaline in special regions, but always showing, throughout at least 

 the greater part of its substance, numerous granulations, which 

 vary greatly in size, from relatively coarse grains to those of the 

 minutest size visible with the power of the microscope used. The 

 most important of these granulations are the so-called "chromatin- 

 grains," which are discussed fully in Chapter VI. ; in this chapter 

 only non-chromatinic granules are dealt with. The coarser proto- 

 plasmic grains may be present in greater or less quantity, or may 

 be entirely absent ; they are to be regarded for the most part as 

 so-called metaplastic bodies that is to say, as stages in, or by- 

 products of, the upward or downward metabolism of the organism. 

 On the other hand, the minute, ultimate granules, or " microsomes," 

 are never absent, except over limited areas, in any sample of proto- 

 plasm. It is on the constant presence of granules that the so-called 

 granular theory of protoplasm, especially connected with the name 

 of Altmann, has been founded. On this view, each minute granule 

 is regarded as an elementary organism, or " biobjast," capable in 

 itself of all vital functions, and equivalent to a single free-living 

 bacterium, just as a single cell of a Metazoan body may be compared 

 with a single Protozoan organism. Protoplasm, on this view, js rer 



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