PROTOZOA 75 



larly in parasitic forms, the nucleus and kinetic elements may 

 divide a number of times before division of the cell protoplasm, 

 so that when the latter does divide a brood of daughter cells 

 results. Such a multinucleated cell is called a somatella. Some 

 unusual types of flagellates possessing two nuclei, e.g., Giardia 

 (Fig. 39), or many nuclei, e.g., Calonympha, have arisen, appar- 

 ently by the development of flagella, be- 

 fore cell division of the somatella has 

 taken place and are interpreted as rep- 

 resenting permanent somatellae. 



Fig. 43— AN ARBOROID COLONY OF MINUTE 



ANIMAL FLAGELLATES, POTERIODENDRON 



PETIO LATUM 



Each cell is attached by a stalk in its individual cup, and 

 each cup is attached by a stalk to the inside of a parent cup 



From a drawing by the author 

 Magnification, 410 



Many of the animal flagellates, like the plant flagellates, 

 form colonies as a result of incomplete separation at division 

 or by association in a common gelatinous matrix after division. 

 Individuals frequently grow out on long stalks which remain at- 

 tached and which expand into cups, within which the monads are 

 fixed (Fig. 43). Or the minute cells may secrete gelatinous 

 tubes, one for each monad, which may lie parallel to one another 

 or which may diverge at varying angles. One such colonial form, 

 Rhipidodendron, which is quite common in stagnant waters, is 

 made up of parallel or slightly diverging gelatinous tubes col- 

 ored brown or red by iron oxide. Because it has a single 'monad 

 at the extremity of each tube, and because of the parallel arrange- 

 ment of the tubes, it is called the organ-pipe monad. 



Some forms (Hypermastigidae) have more than a hundred 

 flagella. The Hypermastigidae are interesting because without 

 them white ants cannot live (see page 102). 



