COLONIAL PROTOZOA 



Among the Protozoa are found some forms in which the 

 individual cells do not separate immediately after fission but re- 

 main attached to form either temporary or permanent groups of 

 cells called colonies. The chief point wherein these protozoon 

 colonies differ from true many-celled animals, the Metazoa, lies 

 in the fact that while certain cells may be set aside and special- 

 ized as sex cells or gametes for reproduction, all the other cells of 

 the body, the somatic cells, remain similar one to another, i. e., 

 they lack histological differentiation. 



Pandorina and Eudorina are two examples of such colonies 

 consisting of a small number of similar cells held together by a 

 jelly-like substance called the matrix. In reproduction, each cell 

 of the colony may continue to divide by simple fission until it 

 forms a new colony. This is the asexual method of reproduction. 

 Some of the colonies may produce male sex cells and others 

 female sex cells. In these cases a male gamete must unite with a 

 female gamete to form a single cell called a zygote which is the 

 starting point of a new colony. This is the beginning of true 

 sexual reproduction. 



Observe under demonstration microscope stained mounts of 

 Eudorina and Pandorina. Then as you take up the study of 

 Volvox note how these serve as a transition from the forms with 

 no colonial tendencies, such as Paramecium and Euglena, to the 

 more highly specialized condition found in Volvox. 



VOLVOX 



Classification: — Phylum Protozoa, Class Mastigophora, 

 Order Phytomonadina. 



1. Read the entire Volvox outline before beginning to 

 study the prepared slide. 



2. In Volvox, is found a still higher type of colony life 

 where several hundred, or even thousands, of cells have become 

 associated to form a single layer of cells over the surface of a 



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