28 



MU1.TICELLULAR ORGANISMS 



lives. In the higher types of simple animals and plants, 

 however, the division products remain attached, and form 

 colonies in the shape of threads, sheets, or solids of vari- 

 ous form, depending upon the direction of the cleavage 

 and the subsequent arrangement of the cells. Among 

 the simplest of these colonial species is Gonium (Fig. 6), 

 occurring commonly in fresh water. Here the single 

 parental cell divides, the two products remain attached, 

 re-divide, and in this fashion reach a sixteen-cell stage 

 with the cells forming a plate. Every member of the 

 colony, bearing locomotor whips, or flagella, that operate 



Fig. 6. — Colonial Organisms, 

 views of Gonium. 



A, Vol vox; B, C, top and side 



like cilia, is precisely like its fellow in form and function. 

 It is important to note that the colony may be broken up 

 and each cell continue to exist. As a matter of fact the 

 cells do become dissociated at the time of reproduction, 

 each forming a daughter colony. 



VoLvox. — In Volvox (Fig. 6), a higher type of 

 colonial organism, the body comprises many cells — in 

 some species thousands in number — imbedded in a jelly- 

 like substance and arranged in the form of a hollow 

 sphere. Each cell is egg-shaped and the greater number 

 carry flagella whose combined action rolls the association 



