The Hydra. 



13 



batantB had to be moved, and the stirring of the water shook the 

 exbansted animals free from each other. 



The hydra is extremely sensitive, and contracts at once 

 if touched. The variety of shapes it can assume, espe- 

 cially when digesting its food, is very wonderful. 



Fig. 4-6. 



There are buds on some of the hydras, which at first 

 look like knobs, then grow larger, form tentacles (Fig. 

 4 — 6), and gradually pinch themselves o£E from the 

 parent, and set up for themselves. In the autumn eggs 

 are produced (Fig. 1 a), which live through the winter. 



Fig. 7-11. 



In 1744, Trembley, a watchmaker of Geneva, performed 

 a remarkable series of experiments upon hydras. He 

 found that they can move about by turning somersaults 

 (Figs. 7-11) ; that if cut in small slices, each slice becomes 



