Rotifers 



177 



The Rotifers constitute a large group of minute 

 animals, most characteristic of fiesh-water. They 

 abound in all sorts of situations, and present an extra- 

 ordinary variety of forms and habits. Their habits 

 vary from ranging the open lake to dwelling symbioti- 

 cally within the tissues of water plants ; from sojourning 

 in the cool waters of peren- 

 nial springs, to running a 

 swift course during the tem- 

 porary^ existence of the most 

 transient pools. They even 

 maintain themselves in rain- 

 spouts and stone urns, where 

 they become desiccated with 

 evaporation between times of 

 rain. 



Rotifers are mainly micro- 

 scopic, but a few of the larger 

 forms are recognizable with 

 the unaided eye. Often they 

 become so abundant in pools 

 as to give to the water a tinge 

 of their own color. Grouped 

 together in colonies they be- 

 come rather conspicuous. 

 The spherical colonies of Cono- 



chilus w^hen attached to leaf-tips, as in the accom- 

 panying picture, present a bright and flower-like 

 appearance. Entire colonies often become detached, 

 and then they go bowling along through the water, 

 in a most interesting fashion, the individuals jostling 

 each other as they stand on a common footing, and 

 all merrily waving their crowns of cilia in unison. Often 

 a little roadside pool will be found teeming with the 

 little white rolling spheres, that are quite large enough 

 to be visible to the unaided eye. 



Fig. 85. Three colonies of the 

 rotifer, Conochilus, attached 

 to the tips of leaves of the 

 pond- weed, Nais, 



