HYDRA. 189 
it fast till the polype can master and devour it. This is 
by far the most common Hydra in the west of Scotland. 
It is so common, indeed, that if in summer or autumn you 
take up at random a handful of duckweed or pond-weed 
(Lemna or Potamogeton) from a ditch or stagnant pool, and 
put it in a glass vase, you are almost sure to see that you 
have captured several green Hydre. Their tentacula, 
however, though not some inches long, like those of other 
species figured by Trembley, can be extended by the creature 
so as to be fully the length of.the body. ‘I imagined those 
polypes owed their green colour to some particular food, such 
as weeds, etc., and that they would lose it upon being kept 
to worms; but I find myself mistaken, for they retain their 
greenness after some months as well as ever, and are now 
grown of a moderate size, extending sometimes three- 
quarters of an inch; their tentacula are also lengthened 
very much to what they were, and are of a lighter green 
than the body, their number, eight, nine, or ten. The tail 
is very little slenderer than the body, but more spread at 
the end than the tails of the other kinds.” (Baker, 1743.) 
Pallas says, that the offspring are produced from every part 
of the body. Blainville thinks he has remarked that they 
spring always from the same place, though he owns that 
