CHAPTER VIII 



Phylum Trochelminthes 



The Rotifera, sometimes called "wheel animalcules," belong to 

 a group, the exact relationship of which is unknown. They have 

 sometimes been classed with the worms. The majority of them are 

 free swimming and move by means of a trochal disc (Fig. 51). In 

 other forms a telescopic tail aids the animal in performing looping 

 movements similar to those of a leech. Przibram states that, in the 

 Rotifer, growth is not followed by the formation of new cells, but 

 the size of single cells increases. 



Rotifera are for the most part found in fresh water, although 

 a few are marine. When the water dries up, the thick-shelled 

 winter eggs of certain rotifers may be dispersed by the wind or by 

 animals. They are able to survive freezing temperature. 



Eichhorn (1781) describing Floscularia says: "Now I come to a 

 very wonderful animal, which has often rejoiced me in my observa- 

 tions: I call it the Catcher: extraordinarily artistic in its structure, 

 wonderful in its actions, rapid in capturing its prey." (From H. S. 

 Jennings, in Ward and Whipple's "Fresh Water Biology," published 

 by John Wiley and Sons, Inc., 191 8.) 



Rotifera have an elongated body^ with a tail-like appendage, the 

 foot^ which commonly ends in two pointed toes. Pedal cement 

 glands aid in attachment. The digestive syste^n is well developed 

 with an anteriorly situated inouth which is between the ciliated 

 trochal discs and leads into a muscular pharynx. At the lower end 

 of the pharynx is the gizzard or mastax which has chitinous teeth. 

 (See Gosse, "Structure, Functions and Homologies of the Manduca- 

 tory Organs in the Class Rotifera." Phil. Trans., 1856.) 



The excretory system is relatively simple, with paired convoluted 

 tubes, the kidneys, which open directly or indirectly into the cloaca. 

 The nervous system consists of the dorsally situated brain, with 

 nerves given off to the corona, the muscles, integument, and sense 

 organs. Two large nerves are given off laterally from the brain 

 and each divides into a ventral and a lateral longitudinal trunk. 

 The sense organs consist of the tactile and olfacto-gustatory an- 



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