IV] AND STRUCTURE OF THE CELL 327 



hypothesis. The round drop of clear fluid which forms the centre 

 of the aster grows as the aster grows, fluid streaming towards it 

 from all parts of the cell along the channels of the astral rays. 

 The cytoplasni between the rays is in the gel state, but gradually 

 passes into a sol beyond the confines of the aster. Seifritz asserts 

 that the substance of the centrosphere is *'not much more viscous 

 than water," but that the wedges of cytoplasm between the inwardly 

 directed streams are stiff and viscous*. 



After the centrosome divides we have two oscillating bodies 

 instead of one; they tend to repel one another, and pass easily 

 through the fluid centrosphere to the denser layer around. But 

 now the new centrosomes, on opposite sides of the centrosphere, 

 repel, each on its own side, the disperse particles of the denser zone ; 

 and two new asters are formed, their rays marked by the streams 

 coursing inwards to the centrosome-foci. Thus the amphiaster 

 comes into being; it is not that the old aster divides, as a definite 

 entity; but the old aster ceases to exist when its focus is disturbed, 

 and about the new foci new asters are necessarily and automatically 

 developed. Again this hypothetic account taUies well with Chambers's 

 description. 



The same attractions and repulsions should be manifested, perhaps 

 better still, in whatsoever bodies he or float within the cell, whether 

 liquid or solid, oil-globules, yolk-particlea, mitochondria, chromo- 

 somes or what not. A zoned, concentric arrangement of yolk- 

 globules is often seen in the egg, with the centrosome as focus; 

 and in certain sea-urchin eggs the mitochondria gather around 

 the centrosome while the amphiaster is forming, collecting together 

 in that very zone to which Chambers ascribes a semi-rigid or viscous 

 consistency!. The Golgi bodies found in various germ-cells are at 

 first black rod-hke bodies embedded in the centrosphere ; they 

 undergo changes and complex movements, now scattering through 

 the cytoplasm and anon crowding again around the centrosome. 

 Some periodic change in the density of these bodies compared with 



♦ Cf. W. Seifritz, Some physical properties of protoplasm, Ann. Bot. xxxv, 

 1921. Wo. Ostwald and M. H. Fischer had thought that the astral rays were 

 due to local changes of the plasma-sol into a gel, Zur physikal. chem. Theorie der 

 Befruchtung, Pfluger's Archiv, cvi, pp. 2^3-266, 1905. 



t Cf. F. Vejdovsky and A. Mrazek, Umbildung des Cytoplasma wahrend der 

 Befruchtung und Zelltheilung, Arch. f. mikr. Anat. LXii. 431-579, 1903. 



