SOCIAL " CROWNED HEADS." 1^7 



Megalotrocha. In both the young brood is often 

 separated from the parental, surroundings, and for 

 a time lives a free rolling life, and may in this 

 condition be easily mistaken for Conochilus ; also 

 with the Megalotrocha, if a portion of even a 

 mature colony be separated and detached, it at 

 once commences, though rather awkwardly, a slow 

 and revolving motion. Indeed, a social colony, 

 whether of Rotifers or any other form of life hav- 

 ing a ciliated surface or disc, must by the action 

 of this cilia, which creates vortices and whirlpools 

 in the water, tend to produce a revolving motion of 

 the whole colony. 



Nothing can be gained by this motion with 

 either Megalotrocha or Lacinularia, whose habitat 

 is moving water, and consequently we find that 

 they soon settle down to a fixed and permanent 

 attachment ; but in the case of Conoc/tilus, cast off 

 from the running stream and confined in still water, 

 this motion, by aerating the water, would be the 

 natural compensation for the loss sustained, and if, 

 as may be presumed, some sensations of a plea- 

 surable nature were added to the undoubted physical 

 advantage ; this motion would be perfected by in- 



