64 LIFE AND HER CHILDREN. 
animals of the sea, are devoured by this ferocious 
lasso - thrower as he moves lazily through the 
water expanding and contracting the rim of his dome ; 
and if it were not that he and his fellows are the 
chief food of whales and porpoises, they would com- 
mit terrible havoc in the ocean, as they travel in 
shoals of thousands together. 
And now at certain seasons of the year, when at 
night the sea glows with their phosphorescence,"" some 
of these large wanderers drop from under their huge 
umbrella something which looks like a shower of 
dust. This shower is composed of a number of 
minute jelly-bodies (a, Fig. 24) swimming by means 
of lashes or cilia, and something like those which come 
from a sponge (see p. 38). They have been hatched 
from eggs within the umbrella of the jelly-fish, and are 
setting off into life for themselves. After a few days 
four curious knobs (b, Fig. 24) begin to appear upon 
them, and these increase every day till at last the 
swimming animal settles down on a rock and becomes 
a small hydra feeding peacefully upon minute sea- 
animals by means of its tender threads. 
This then is the young of our jelly-fish, a common 
hydra like that of the pond ! Moreover, this young 
hydra seems to forget all about its wandering parent- 
age, and often goes on for several years budding into 
other hydras, and living as though it had never had 
anything to do with a jelly-fish. 
But at last one day a change comes over some of 
* The phosphorescence is due to a glutinous fluid exuded from the 
umbrella. This fluid, when squeezed from a large jelly-fish into twenty- 
seven ounces of cows' milk, made it so phosphorescent that a letter could 
be read by the light at a distance of three feet. 
