Page:Popular Science Monthly Volume 33.djvu/768

 a root (Fig. 18); and a bud, m, soon grows out from it to form the first feeding hydra, which soon acquires a mouth (Fig. 19, l) and tentacles, i, and begins to capture and digest food and to accumulate a reserve of nutriment, while the root continues to throw



out new buds, as shown in Fig. 18 at m. For a long time all the buds become feeding hydras; but at last, when the mouths are numerous enough, buds which remain mouthless are formed, and become the blastostyles or jelly-fish producers. The following diagram shows the life-history of Eutima:

Diagram No. 1, which was given in the beginning of this article, to illustrate the life of Dysmorphosa, shows the next stage in the process of complication, and a comparison will show that it is derivable from Diagram VI by slight changes, just as VI is derivable from V, and this from the preceding, and so on until finally we reach a simple, direct life-history, in which each egg produces one adult, which passes through a transitory larval hydra stage.

Forty years ago, a zoölogist of the old school might have believed that the life-history of Dysmorphosa has always been complex, and that of Liriope always simple; but the doctrine that all the representatives of any great group of animals owe their common characteristics to descent from a common ancestor is one of the fundamental principles of modern elementary zoölogy, and as this doctrine forms the basis rather than the aim of this article, I assume, without discussion, that the remote ancestors of Liriope