56 LIFE AND HER CHILDREN. 
It is scarcely possible to collect seaweed on any 
coast without finding upon it what look like minute 
plants (Fig. 21) with frequent joints. Some of these, 
which are formed of chalk, are true plants, but others, 
which are yellowish and horny, are no less certainly 
animals, and you may soon detect these by means of 
a magnifying glass, for they will bear at each joint 
a little cup (c c\ and if you could watch these cups 
The Sea-Oak.* Adapted from Hincks. 
I. The animal-tree growing of the natural size. 2. A piece of one 
branch enlarged, showing the animal b stretching out of the horny cup 
c, and one of the egg-sacs s. 
when the creature is alive, you would see out of each 
one from 12 to 1 6 transparent tentacles (b b} sweep- 
ing round in search of food. 
This tree-like stem is in fact the home of a hydra 
of the sea. The creature itself is like the pond hydra, 
only that its buds do not fall off but continue to live 
* Sertnlaria plumula. 
