3l8 SOME PROBLEMS OF CELL-ORGANIZATION 



fibres with the respective centrosomes. Heidenhain, adopting the 

 first of these assumptions, builds upon it an elaborate theory of cell- 

 polarity and cell-division already considered in part at pages 103-105. 

 Sometimes the astral rays ('* organic radii ") retain their radial arrange- 

 ment throughout the life of the cell (leucocytes, Fig. 49) ; more com- 

 monly they are disguised and lost to view in the cytoplasmic meshwork. 

 All, however, are equal in length and in tension — assumptions based 

 on the one hand on the occurrence of concentric circles of microsomes 

 in the aster, on the other hand on the analogy of the artificial model 

 described at page 104. Biihler ('95) and Kostanecki and Siedlecki 

 ('97) likewise unreservedly accept the view that besides the centro- 

 some the entire system of '' organic radii," including astral rays, 

 mantle-fibres, and central spindle-fibres, persists in the resting cell in 

 modified form, and is centred in the centrosome. Kostanecki finally 

 ('97) takes the last step, logically necessitated by the foregoing con- 

 clusion, and apparently supported also by the crossing of the astral 

 rays opposite the equator of the spindle and the relations of their 

 peripheral ends, concluding that the monocentric astral system is con- 

 verted into the dicentric system (amphiaster) by longitudinal fiSsion 

 of the rays} Thus the entire mitome of the mother-cell divides into 

 equal halves for daughter-cells ; and since the radii consist of micro- 

 somes, each of these must likewise divide into two.^ 



Could this tempting hypothesis be established, Roux's interpretation 

 of nuclear division (p. 224) could be extended also to the cytoplasm ; 

 and the aster- and amphiaster-formation, with the spireme-forma- 

 tion, might be conceived as a device for the meristic division of the 

 entire cell-substance — a result which would place upon a substantial 

 basis the general corpuscular theory of protoplasm. Unfortunately, 

 however, the hypothesis rests upon a very insecure foundation : first, 

 because it is based solely upon the fibrillar theory of protoplasm ; 

 second, because of the very incomplete direct evidence of such a 

 splitting of the rays ; third, because there is very strong evidence that 

 in many cases the old astral rays wholly disappear, to be replaced by 

 new ones.^ We may best consider this adverse evidence in connec- 

 tion with a general account of the opposing archoplasm-hypothesis. 



2. The Archoplasm Hypothesis 



Entirely opposed to the foregoing conception are the views of 

 Boveri and his followers, the starting point of which is given by 



1 '97, p. 680. 



2 This view had been definitely stated also by O. Schultze in 1890. 



^ There is, however, no doubt that the aster as a whole does, in some cases, divide into 

 two — for instance, in the echinoderm-egg. Fig. 95. 



