CELL DIVISION 



II 



until the whole equatorial zone is traversed by them (in g and h) . 

 The fibers thicken in the equatorial area and the thickenings fuse 

 together, forming a closed membrane known as the cell-plate 

 (progressive stages in g, h, and i). This is a plasmatic mem- 



Mm 



Fig. 3. — Semi-diagrammatic representation of nuclear and cell division, a, resting 

 cell ready to begin division; b, the nuclear reticulum is assuming tiie form of a thickened 

 thread, and the cytoplasm at opposite poles is becoming thread-like to form the spindle 

 fibers; c, the nuclear thread has divided longitudinally through the middle, and the spindle 

 fibers have become more definite; d, the nuclear membrane and the nucleolus have dis- 

 appeared, and the nuclear thread has become segmented into chromosomes which are 

 assembling at the equator of the cell. All of the phases of division thus far are called 

 prophases, e, the metaphase, where the longitudinal halves of the chromosomes are being 

 drawn apart preparatory to their journey toward the opposite poles;/, the anaphase, or 

 movement of the chromosomes toward the poles, is about completed, connecting fibers 

 extend from pole to pole; g, telophase where the chromosomes have begun to spin out in 

 the form of a nuclear reticulum. The connecting fibers have begun to thicken in the 

 equatorial plane ; h, the connecting fibers have spread out and come into contact with the 

 wall of the mother cell in the equatorial plane, . and the thickening of the fibers throughout 

 this plane has made a complete cell plate within which the dividing wall will be produced ; 

 i, a nuclear membrane has been formed about each daughter nucleus, and the dividing cell 

 wall is completed. The two daughter cells are now ready to grow to the size of the parent 

 cell in a, when the daughter nuclei will appear as does the nucleus there. AH highly 

 magnified. 



