SECT. in. COMPO UXD FRESH- WA TER HYDR&. 8 5 



cess, which so closely resembles the budding of plants, 

 must be regarded as a modification of the ordinary 

 nutritious process. The same may be said of the power 

 of reparation, which every animal body possesses in a 

 greater or less degree, but which is most remarkable 

 among the lower tribes, for when an entire member is 

 renewed, or even when the whole body is regenerated 

 from a small fragment, which is the case in many po- 

 lypes, it is by a process exactly analogous to that which 

 takes place in the reparation of the simplest wound in 

 our own bodies, and which is but a modification of the 

 process that is constantly renewing, more or less rapidly, 

 every portion of our frame. 



There is but one species of the single colourless Hydra, 

 but there are four compound fresh-water Hydrse in Eng- 

 land the rubra, viridis, vulgaris, which is of an orange 

 brown, and the fusca. They have coloured particles, 

 either imbedded in their external coat, or immediately 

 under it. The Hydra viridis and H. vulgaris have short 

 tentacles, whilst H. fusca, which is a rare animal, has 

 arms from seven to eight inches long, and so contractile, 

 that they can shrink into the space of small tubercules. 

 All these four Hydrse are compound and permanently 

 arborescent animals ; each springs from one individual 

 hydra of its own race, which increases in length and 

 forms the stem, while young ones spring from it and from 

 one another consecutively, like the compound branches 

 of a tree. The numerous tentacles that hang down like 

 fishing lines, thickly covered with thread-cells and their 

 envenomed darts, catch prey for the whole colony, because 

 the communication between the stomachs of the young 

 polypes or Hydras and that of their parent is never cut 

 off, as it is when the offspring is deciduous ; but tubes 

 from the base of each individual Hydra or polype, pass- 

 ing through the stalks and branches of the living tree, 

 unite their stomachs with the stomach or assimilating 



