GROWTH AND REPRODUCTION 759 



the cell will divide. The spindle furnishes the path along which the 

 chromatin filaments move, and probably marks out the lines of chemico- 

 physical strain. These lines of stress are very like those assumed by 

 iron particles within a magnetic field (Fig. 463). Mitotic-like figures 



FIG. 464. LINES OF STRESS IN LIVING DIVIDING OVUM oe TOXOPREUSTES. 

 (Verworn, after Wilson.) 



The circumjacent fluid is of intermediate density. 



can be produced by placing droplets of certain solutions coloured with 

 China ink on the surface of other solutions of greater density. Such 

 figures may be well seen in many growing plants cells for example, 

 in those of the root-tip of the hyacinth. 



FIG. 465. HYDROID (Tubularia) GENERATING A HEAD AT EACH END OF A FRAG- 

 MENT OF THE STEM SUSPENDED IN WATER. (Redrawn after Loeb, from Wilson's 

 " The Cell," etc.) 



In many animal cells, especially ova which divide as the result of 

 fertilization, the centrosome divides into two daughter centrosomes, 

 which move to opposite sides of the nucleus and become surrounded 

 by rays to form an achromatic spindle connecting the two daughter 

 centrosomes, around the equator of which the chromosomes arrange 

 themselves (Fig. 467). In the anaphase stage the divergence 



