MITOSIS 53 



small percentage will contain the entire spindle. Most of the 

 sections passing through the spindle will cut it at various angles 

 to its chief axis and will thus include only a portion of the 

 mitotic figure. 



In sections of cells undergoing mitosis study the following 

 stages in the process of mitosis and make one or more drawings 

 of each. Divide the page into six parts and place drawings in 

 proper order as the difiPerent stages are found. 



In this exercise, keep the drawings in sequence, six drawings 

 to a page. Prepare a sheet of drawing paper by ruling a 

 line down the middle of the page and then two cross lines to 

 divide the sheet into six equal parts. This exercise requires 

 5 drawings. Before making any drawings, number the posi- 

 tions for all 5 figures by labelling the respective squares "Fig. 

 1," "Fig. 2," etc., consecutively. Then as individual stages are 

 located each should be drawn in its proper position in the 

 series. The unused space at the end of the series may be used for 

 drawings of demonstrations or additional stages if time permits. 



Caution ! Mitosis follows much the same series of steps or 

 stages in many diflPerent kinds of animal and plant tissues. 

 However, there are numerous individual points of difiPerence in 

 the details of the process for every organism. Developing eggs 

 of the roundworm (Ascaris megalocephala) and those of the 

 starfish, sea urchin, and the marine worm (Cerebratulus) are 

 favorable sources for the study of mitosis. The spermary of a 

 salamander and of certain species of crayfishes and grasshop- 

 pers are also valuable for the study of mitosis. In the labor- 

 atory study be sure to draw figures of mitosis characteristic of 

 the particular kind of cells provided by your instructor, with- 

 out regard for the generalized diagrams of mitosis. 



For the resting stage (Fig. 1) and for the telophase (Fig. 5) 

 draw the entire cell. In the remaining stages draw the nuclear 

 structures and mitotic figure only. 



1. Resting Stage. Chromatin scattered throughout the 

 nucleus in the form of small granules. Fig. 1, 



