VOLVOX * 



1. Place a drop of water containing Vol vox on a slide. Examine, with- 

 out cover glass, under the low power. Each Volvox colony will be seen as a 

 more or less transparent, hollow sphere. Note that each colony is com- 

 posed of a large number of tiny, greenish bodies (somatic cells) which are 

 embedded in a supporting intercellular material. In many cases a number 

 of smaller spheres are enclosed within the transparent walls of the parent 

 colony. These are the daughter colonies, and they have arisen by 

 repeated divisions of asexual reproductive cells (parthenogonidia) which 

 develop without fertilization. Make an enlarged drawing of a Volvox 

 colony to show the structure as observed. 



2. Carefully place a cover glass on the preparation and examine with 

 the high power. Focus carefully on the wall of a colony and study the 

 somatic cells. Note that the cell body of each consists of an irregular- 

 shaped, greenish-colored bit of cytoplasm. Branching out from each cell 

 body are very fine cytoplasmic strands which run through the intercellular 

 material and connect with adjacent cells so that there is a protoplasmic 

 continuity throughout the colony. Each cell also possesses two flagella 

 which project to the exterior and aid in the movements of the colony. 

 Draw a portion of the wall of the colony giving a view of the cells as out- 

 lined above. 



3. Focus on one of the enclosed asexual daughter colonies. Note the 

 comparatively small amount of intercellular material between the cells of 

 a young colony as compared with the parent colony. Draw a portion of 

 the wall of the daughter colony. 



4. If material is available, study a Volvox colony in which germ cells 

 are present. In such a colony note (a) a spermary, which consists of a 

 large number of sperm cells or male gametes, grouped together to form 

 a rather flat plate, and (b) an ovary of about the same size as the spermary, 

 but which contains only a single egg cell, or female gamete. Both the 

 spermaries and ovaries are embedded in the wall of the colony. Draw to 

 show the structure as observed. 



1 B. pp. 34-38. 



261 



