ZOOLOGY. 29 
digestive cavity. Such beings as the Campanula produce, 
through budding, beautiful little jelly-fishes, which swim 
freely about. They in their turn produce eggs, from which 
spring the stationary colonies of Hydre. There is an alter- 
nate generation, Campanularie producing jelly-fish, jelly- 
fish producing Campanulariz. We see the Hydra living 
as an independent organism—the Hydra of our fresh-water 
ponds—and ina transitory stage, as the Campanula. Some- 
times a colony of these Hydroids form a freely swimming 
organism, as the Portuguese man-of-war. The Ctenophore, 
or comb-bearing jelly- fishes, pure as crystal and transparent 
as glass, are characterized by their organs of motion, which 
are eight delicate combs, by the graceful movement of 
which the Beroes and Cydippe glide through the sea. 
They are intermediate in some respects between the Anem- 
ones and common jelly-fish (Aurelia). By glancing at 
Tree II. we see the probable origin of the Anemones, Corals, 
and Jelly-fish in the Sponges, the Anemones and Corals 
coming from the hard sponges, the fossil forms of which, 
like Ventriculites and Guettardia (Figs. 13, 17), closely re- 
semble in the arrangement of their chambers those of the 
Anemone and Coral. By comparing the transverse section 
of a sponge (Fig. 22) with that of the jelly-fish (Fig. 21), we 
see that the canals of the sponge are the same as those of 
the jelly-fish, though more simple in their arrangement. 
Though objections have been, and will be, raised to this 
view of the origin of the Actinozoa and Hydrozoa, that they 
have so descended from stationary beings the Anemones 
and Hydroid polyps are the living proofs. That these 
stationary ancestors were sponges, or beings allied to them, 
is rendered very probable by the harmonious evidences of 
the structure, development, and fossil remains of the entire 
group. 
We will now leave the Ccelenterata, considered as a 
distinct division of the animal kingdom on account of its 
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