48 LABORATORY DIRECTIONS 



matic cells should be shown but all of the clusters of micro- 

 gametes should be drawn in outline. Detailed structure of at 

 least one cluster of microgametes should be brought out. 



The two kinds of female colonies are much alike in struc- 

 ture. In them, the distance between two somatic cells is usually 

 not more than the diameter of a single somatic cell. There is 

 no reliable constant difference in the appearance of either the 

 somatic cells or of the macrogametes in the parthenogenetic fe- 

 male colonies and the true sexual female colonies. Observations 

 upon living material have demonstrated that the chief difference 

 lies in the number of gametes. True sexual female colonies of 

 this species contain sixteen or more gametes while female colo- 

 nies containing twelve or fewer macrogametes are parthenoge- 

 netic female colonies. 



Make a drawing of each kind of female colony showing 

 colony wall in optical section and showing in outline the total 

 number of macrogametes characteristic of each. Show at least 

 one macrogamete in detail. 



See demonstration of zygotc and draw, about 20 mm. in 

 diameter. 



MITOSIS 



Reproduction of the Cell 



All living organisms are built up of minute units called cells. 

 The power of an organism to reproduce itself is dependent upon 

 the ability of these protoplasmic units to divide and thereby re- 

 produce other cells. Mitosis is the name applied to the long se- 

 ries of intricately correlated changes which the nucleus undergoes 

 during the division of the cell. Cell division is especially active 

 and conspicuous in the early development of an individual from 

 a fertilized egg. The structures involved in mitosis are so minute 

 that they can not be studied easily in entire cells, consequently 

 cells undergoing mitosis are preserved and cut into thin slices 

 (sections) by the use of an instrument called the microtome. 



