rt ON ANIMAL LIFE 109 
Fig. 4 represents the Medusa or free form 
of this beautiful species. 
If we pass to another 
great group of Zoophytes, 
that of the Jelly-fishes, 
we have a very similar 
case. For our first knowl- 
edge of the life-history 
of these Zoophytes we 
are indebted to the Nor- 
wegian naturalist Sars. 
Take, for instance, the 
common Jelly-fish (Me- 
dusa aurita) (Fig. 5) of Fig. 4.— Bougainvillea 
— oF ea ) ( 8 ) fruticosa, Medusa-form. 
The egg is a pear-shaped body (7), covered 
with fine hairs, by the aid of which it swims 
about, the broader end in front. After a 
while it attaches itself, not as might have 
been expected by the posterior but by the 
anterior extremity (2). The cilia then dis- 
appear, a mouth is formed at the free end, 
tentacles, first four (7), then eight, and at 
length as many as thirty (¢), are formed, and 
the little creature resembles in essentials the 
freshwater polyp (Hydra) of our ponds. 
