128 



THE PROTOZOA 



equally represented in the daughter-cells, or they may remain whole, 

 going to that daughter-cell to which they are nearest, the other cell 

 forming a new set. The flagellum, in some cases, is also divided 

 throughout the entire length, although in other cases it is thrown off 

 before division takes place, new ones being formed by the daughter- 

 cells. In many cases new flagella, as well as all of the important 

 structures, are pre-formed before division. Such divisions may take 

 place while the organisms are moving freely about in the water, or 



Fig. 72. Gonium pectorale O. F. M. [STEIN.] 



while they are quiescent and inclosed in a firm cyst. ^S a rule, 

 division is longitudinal, but cases are well known where it is trans- 

 verse (in most of the Dinoflagellidia, in Epipyxis, Stylochrysalis, 

 Oxyrrhis, etc.). 



Some forms (e.g. Traohelomonas) reproduce by simple division 

 while still within the shell, one half making its way out through 

 the neck or flagella-opening, leaving the other in possession of the 

 original home. 



Colony-formation is' closely connected with the process of simple 

 division, and nowhere among the Protozoa does it reach such high 

 grades of differentiation as in this class. The colonies of this group 



