THE GROWTH OF JELLY-FISHES. 



749 



and Dysmorpliosa 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 



Fig. 19.— Young hydroid colony of Eutima. 



this ancestor, the conditions of life became more and more favor- 

 able for the larvse, and as successive generations of larvae became 

 more and more adapted to these conditions, the larval life gradu- 

 ally 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 larvse, which em- 

 body all that is most distinctive and characteristic of the species. 



