Page:Popular Science Monthly Volume 33.djvu/769

Rh and Dysmorphosa were the same, and that all the life-histories which have been described are modifications of that which was exhibited by this ancestor.

The series which has been given shows that this ancestor must have developed directly from the egg, its adult stage must have been the most important part of its life, and the hydra stage only a transitory larval condition. As, in certain lines of descent from



this ancestor, the conditions of life became more and more favorable for the larvæ, and as successive generations of larvae became more and more adapted to these conditions, the larval life gradually increased in length and importance, and threw the adult sexual stage more and more into the background, until, in the case of Dysmorphosa, we have a colony of long-lived larvæ, which embody all that is most distinctive and characteristic of the species.