THE WATER-HYDRA. 171 



surface is below the level of the tide and the sea fenced 

 off by dykes, the water-shrew is hunted as one of the 

 most dangerous enemies of the country. In Britain it is 

 not much heeded, though dogs search for it, and some- 

 times make their appearance with it hanging to their 

 noses. The female shrew is said to produce nine young 

 in a litter, and to have several litters in the course of 

 the year. 



There is one very singular aquatic animal on which 

 the shrew feeds an animal at the very lowest extremity 

 of animated life an animal without organs of loco- 

 motion, and, indeed, hardly organized, and yet it preys 

 upon animal food. That is the fresh-water polypus, 

 (hydra viridis). It is found sticking to plants, in slow 

 running shallow streams of fresh water, and it is by no 

 means uncommon. It consists of a single sack or 

 tube, about an inch in length, and open at both ends. 

 Its substance is of a jelly-looking matter, mixed 

 with small glandular bodies. It is furnished with 

 filaments, or tentaculce, by means of which, it lays 

 hold of small molluscte, the remains of which are, 

 after digestion of the soluble parts, discharged by the 

 mouth. Simple as it seems, however, it can make a 

 sort of progressive motion, in which it fastens its head 

 and tail like a leech. It can even rise to the surface, 

 where, opening the tail like a funnel, it holds itself 

 suspended, its body with the air in the funnel being 

 lighter than the bulk in water. It is chiefly when in 

 this state of exhibition that it is hunted and captured 

 by the shrew. 



The means of reproduction in this apparently very 

 simple animal are very singular. Little buds appear 



