STRUCTURAL BASIS OF PROTOPLASM 



27 



made.^ On the whole, the present drift of opinion is toward the 

 conclusion that none of the above interpretations has succeeded in 

 the attempt to give a universal formula for protoplasmic structure ; 

 and many recent observers have reached the conclusion, earlier advo- 

 cated by Kolliker ('89), that the various types described above are 

 connected by intermediate gradations and may be transformed one 

 into another, in different phases of cell-activity. Unna ^95), for 

 example, endeavours to show how an alveolar structure may pass into 

 a sponge-like or reticular one by the breaking down of the inter- 



c ■ 





"oQo°' 



o •°°' . 



Fig. II. — (a) Protoplasm of the egg of the sea-urchin (Toxopneustes) in section showing 

 meshwork of microsomes; {b) protoplasm from a living star-fish egg {Asterias) showing alveolar 

 spheres with microsomes scattered between them ; fc) the same in a dying condition after crush- 

 ing the egg ; alveolar spheres fusing to form larger spheres ; {d) protoplasm from a young ovarian 

 egg of the same. (All the figures magnified 1200 diameters.) 



alveolar walls. Flemming, for many years the foremost and most 

 consistent advocate of the fibrillar theory, now admits that protoplasm 

 may be fibrillar, alveolar, granular, or sensibly homogeneous,^ and 

 that we cannot, therefore, regard any one of these types of structure 

 as absolutely diagnostic of the living substance. In plant-cells 

 Strasburger^ and a number of his pupils maintain that the " kino- 

 plasm" tp^ 322) or filar plasm, from which the spindle-fibres and 

 ■astrTl rays are formed, is fibrillar, while the " trophoplasm " or 

 alveolar plasm forming the main body of the cell is alveolar, the 

 former, however, assuming the fibrillar structure, as a rule, only 

 during the mitotic activity of the cell. My own long-continued 

 studies on various forms of protoplasm have likewise led to the con- 

 clusion that no universal formula for protoplasmic structure can be 



1 For full discussion, with literature list, see Flemming, '82, '97, i, '97, 2, and Butschli, 

 '92, 2, '99. 2 'g^, I, p. 260. 8 '95. '97. 3. '98- 



