CHAPTER IV 



THE SIMPLER METAZOA 



38. Metazoa. — The Protozoa just studied are single, 

 free, living cells, while the grasshopper is made up of 

 thousands of cells. The grasshopper is called a metazoan 

 (mSt-a-zo'an : Greek, meta, after ; zoon, animal) because 

 there are many cells in its body. The Protozoa and the 

 Metazoa are alike in that both take in food, breathe, give 

 off waste matter, and reproduce their kind. 



There are a number of organisms concerning which 

 scientists disagree as to whether they are plants or animals. 

 In zoology, these forms 

 are known as Colonial 

 Protozoa or simple Meta- 

 zoa. We shall study two 

 of these (Gonium and 

 Vol vox) and then examine 

 the sponges, which all 

 scientists agree are Meta- 

 zoa. 



39. Gonium. — Gonium 

 is an animal made up of 

 sixteen separate cells held 

 together by a mucilage- 

 like secretion of the cells. 



Each cell works independently in getting food, breathing, 

 giving off waste, and in reproduction. The colony 

 moves by lashing the water with long protoplasmic 



55 



Figure 54. — Gonium. 



