PLASM 



the name of metaplasm, or a differentiated plasm, 

 modified by the life-process itself. The true protoplasm, 

 or viscous and at first chemically homogeneous sub- 

 stance, cannot, in my opinion, have any anatomic 

 structure. We shall see, when we come to consider the 

 monera, that very simple specimens of such organisms 

 without organs still actually exist. 



By far the greater part of the plasm that comes under 

 investigation as active living matter in organisms is 

 metaplasm, or secondary plasm, the originally homo- 

 geneous substance of which has acquired definite 

 structures by phyletic differentiations in the course of 

 millions of years. To this modified plasm we must 

 oppose the original simple primary plasm, from the 

 modification of which it has arisen. The name "proto- 

 plasm," in the narrower sense, could very properly be 

 retained for this originally homogeneous form of struct- 

 ureless plasm; but, as the term has now almost lost 

 definite meaning and is used in many different senses, 

 it is, perhaps, better to call this pure homogeneous 

 primary plasm archiplasm. It is still found — firstly, in 

 the body of many (but not all) of the monera, part of 

 the chromacea and bacteria, and the protamcEba and 

 protogenes; and, secondly, in the body of many very 

 young protists and tissue-cells. In the latter case, how- 

 ever, there is already a chemical difiEerentiation of the 

 inner caryoplasm and outer cytoplasm. When we 

 examine these young cells under a high power of the 

 microscope, with the aid of the modem coloring meth- 

 ods, their protoplasm seems to be perfectly homo- 

 geneous and structureless, or, at the most, there are 

 merely very fine granules regularly distributed in it 

 which are believed to be products of metabolism. This 

 is best seen in many of the rhizopods, especially the 

 amoebae, thalamophora, and mycetozoa. There are large 

 amoebae, which thrust out strongly mobile feet from their 

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