Marvels of Pond-Life. 25 



which look like revolving wheels, and a little below 

 them is seen a gizzard in a state of active work. After 

 a little while she swims away with her wheels going, 

 and her tail, forked at the end, is found to be telescopic, 

 or capable of being pulled in and out. As the cilia 

 play, the neighbouring water is agitated, and the mul- 

 titudes of small objects are brought by the whirlpools 

 within her ravenous maw. But the strangest thing of 

 all is that inside her body is seen a young one ; in this 

 case a large and fine infant, which, like " a chip of the 

 old block," imitates the parental motions, thrusts forth 

 its cilia and works its gizzard.* In other genera the 

 eggs are hatched externally, but this one is ovoviparous, 

 and carries its nursery inside. 



A very slight investigation is sufficient to show that 

 in the wheelbearer we have made a great advance 

 towards a higher organization than we discovered in 

 the preceding creatures. We witness what the learned 

 call a " differentiation 3> of parts and tissues, and a 

 "specialization" of organs. The head is plainly dis- 

 tinguishable from the body, the skin or integument is 

 distinctly different from the internal tissues, behind the 

 eyes we can detect a nervous ganglion or miniature 

 brain, the gizzard is a complicated piece of vital 

 mechanism, such as we have not met with before, and 

 in various parts of the transparent inside we see organs 

 to which particular functions are assigned. 



It was at one time thought that Rotifers were her- 



* This was met with in the summer, hut is described here to avoid 

 repetition. I do not know whether the eggs are hatched in very cold 

 weather. 



