4 PROTOPLASM 



taken in interpreting the superficial structure of protoplasm as 

 revealed by the microscope, for the living emulsion presents a 

 variety of forms which look so different from one another that 

 several quite distinct types of structure have been ascribed to 

 protoplasm, when, actually, most of them are different forms of 

 the same thing (page 241). 



Lying beyond the visible structure of protoplasm is another of 

 a quite different character to which many of the more funda- 

 mental properties of living matter owe their existence. Of the 

 nature of this "ultimate" structure we can only conjecture, 

 though our speculations have some foundation. The subject of 

 protoplasmic structure is of such importance that a separate 

 chapter is devoted to it. 



If a superficial examination is made of a protoplasmic mass, 

 say an amoeba or a myxomycete, it will be noticed that there is 

 an inner region of granular matter, which is called endoplasm, and 

 a very narrow border of clear hyaline substance quite free of 

 granules, which is termed ectoplasm. The latter appears to 

 be simply the matrix of the former, which for some reason is 

 kept free of particles at the periphery. Closer examination may 

 reveal a delicate surface layer, the protoplasmic membrane, which 

 dissection shows to be of greater consistency than the inner 

 protoplasm. Plant cells, unlike animal cells, are usually sur- 

 rounded by a heavy wall of cellulose (Fig. 4). In some 

 unicellular organisms (Fig. 28), the outermost membrane assumes 

 the proportions of a tough pellicle, roughly comparable to the cell 

 wall of plants. In plant cells, and possibly also in Protozoa, 

 the protoplasmic membrane lies just beneath the wall or pellicle. 



Biologists are ever trying to distinguish finer differentiations in 

 the structure of protoplasm. The German botanist Strasburger 

 recognized two components, one of which he called kinoplasm, 

 or "active" plasm, and the other trophoplasm, the "nurse," or 

 nutritive, plasm. Scarth and Lloyd have brought Strasburger's 

 terms into use again and emphasized their significance. They 

 defined the kinoplasm as the active irritable component and the 

 trophoplasm as the nutritive substance. A similar differentia- 

 tion between the smallest visible component parts of protoplasm 

 has given rise to the names phaneroplasm, or visible plasm, and 

 cryptoplasm, or hidden plasm, the former being the dispersed 

 phase (liquid globules) and the latter the dispersion medium 



