2 LABORATORY OUTLINES POR EMBRYOLOGY 



Draw a cell in the spireme stage and label the parts. 

 . 3. The spireme becomes thicker and finally separates 

 into a number of pieces called chromosomes. The chro- 

 mosomes are of different shapes, depending upon the 

 species of plant or animal. This stage is known as the 

 astroid stage. If the cell is an animal cell, the centrosome 

 has divided and the parts of it have migrated to opposite 

 sides of the nucleus. From the centrosomes as centers, 

 radiations extend out through the cell. 



Draw a cell in the astroid stage and label all the parts. 



The process up to this point is known as the prophases 

 or preparation stages. 



4. From opposite sides of the nucleus radiations ex- 

 tend across it. These are known as spindle fibers. The 

 chromosomes arrange themselves across the spindle mid- 

 way between the poles. Each chromosome splits longi- 

 tudinally into halves. This stage is known as the meta- 

 phase or middle stage. 



Draw a cell in the metaphase and label all the parts. 



5. One-half of each of the chromosomes passes along 

 the spindle fibers to one pole and the other half to the 

 other pole. When these chromosomes collect around 

 the poles they have the appearance of a double star. 

 This is called the diastroid stage. The diastroid stage and 

 the stages in which the chromosomes are between the 

 center of the spindle and the poles are known as the 

 anaphases. 



Draw a cell with the chromosomes some distance from 

 the poles. Label the parts. Draw a cell in the diastroid 

 stage. Label the parts. 



