87 



form seem to constantly accompany the expression of all 

 the phenomena of active change in living cells, such as 

 growth and division. Networks have been described in 

 nuclei ; the latter are known to expand and contract ; 

 elongate in the direction of certain lines of force ; again 

 withdraw into a globular form, so that Flemming bas 

 proposed the terms diastole and systole for these wonder- 

 ful phenomena, which suggest, if they do not prove, the 

 existence of forces of repulsion and attraction in active 

 labor in the heart of every living cell. We have these 

 phenomena presenting themselves to our vision in the 

 eggs of the oyster and clam. The protoplasm of the egg 

 tremulous with an intense life pent up and energetically 

 trying to unfold itself soon causes the vitelline membrane 

 to quiver and work in rolling waves and the egg assumes 

 very rapidly the form shown in Fig. 4 as ^#^^ 

 seen from below, and Fig. 5 as seen from the (S^-'^m 

 side. The two centres of force or nuclei Mf^'^^y^^K^A 

 are here indicated as two small clear spheres feK;©^^ ■ 2§| 

 near the central part of the two cells which ^^i,^^^^]M 



have been defined by a period of activity just 



past. The forces of growth now remain qui- Figure 4. 



escent for a space, to be exhibited in one 



of their supremest moments of activity 



in Fig. 6, in which a portion of the largest 



cell or megamere is being separted to form 



a smaller cell or micromere. At the same 



Figure 5. time what was the small cell or micromere 



in Fig. 5 is as energetically dividing int( 



two smaller cells or micromeres. 

 result is three micromeres. 

 closely at the 



The 



more 



figure 



Looking 



see wh at ap- 'fe'. • . ■ ■■:■- - ^v 

 pear to be lines of force running from -^|' '^^'^ 

 the faintly marked nuclei of each of two Figure 6. 

 cells to that of two others. The nucleus of the 

 cell is in vital relation with that which is budding from 



arge 



