HYDRAS. 



125 



inch in length, and may be seen suspending them- 

 selves from the under side of the leaves of the duck- 

 weed (Lemnd), or the thread-like leaves of the water 



Fig. 85. 



Hydra viridis. 



crowfoot (Fig. 85). Few fresh-water objects have been 

 more studied, since the first experiments upon them 

 by Trembley a long time ago. When watched with 

 a one-inch power it is surprising what a store of 

 perpetual interest is afforded by them. We can then 

 witness the vegetable process of budding, in which the 

 lower animals are on a par with the higher vege- 

 tables ; we can see the sperm-cells discharged from 

 the tubercles, and notice the young developing 

 through the various stages of growth, until they 

 attain the parental size and shape. 



Minute though these animal and vegetable forms 



