Page:Popular Science Monthly Volume 33.djvu/603

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THE GROWTH OF JELLY-FISHES.
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tory is not a simple process of growth, nor a metamorphosis, like that which occurs among insects.

The caterpillar, which hatches from the butterfly's egg, is perhaps as unlike the butterfly as the hydra is unlike the jelly-fish, Fig. 4, a section, and Fig. 5, a surface view of the larva of Liriope, to show the formation of the mouth, e, and the stomach, d. but it never loses its identity, and the individual which hatches from the egg is the same one which passes through all the caterpillar molts, becomes a chrysalis, and finally escapes as a perfect butterfly, just as the chick which hatches from a hen's egg is the individual which finally becomes a hen and lays eggs in her turn. The growth of the butterfly is accompanied by great and sudden changes from one stage of development to another, but it is simply a process of growth and development, while the life of Dysmorphosa is quite different. The planula, which hatches from the egg, becomes metamorphosed into a root, just as the caterpillar becomes changed into a chrysalis; but here the resemblance stops, for the root goes no further, and it may still remain a root after numbers of jelly-fishes have grown up, laid their eggs, founded new colonies, and died. The feeding hydras and defensive hydras never grow up into jelly-fish, but, as long as they live, continue to perform their proper parts in the colony, and this is equally true of the blastostyles, for these do not become jelly-fish; they simply produce jelly-fish buds, and each one may persist as a blastostyle and continue the process of budding long after the younger buds have completed their history.

In all these particulars the life of Dysmorphosa is a great departure from the normal life-history of animals, for, as a rule, each embryo which hatches from an egg is destined to become an adult animal, and only one.

The simpler aspects of the phenomena of life are older or more