Page:Popular Science Monthly Volume 33.djvu/603

Rh 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, 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