254 University of California PuhUcations. [Zoology 



problem, and that the examination of a single favorable species 

 from different points of view would yield interesting results. 

 Corymorpha is a most satisfactory object for studies of this sort. 

 Its behavior has been investigated somewhat already (Torrey, 

 -.04, :05), with certain unique results. The regenerative de- 

 velopment includes special features of interest to the student of 

 morphallaxis, and will be treated in a paper soon to follow. Thti 

 present paper is concerned with the development from the egg, 

 especially those phases of post-embryonic life which are also rep- 

 resented in the regeneration of the adult, such as the changes 

 resulting in the establishment of the specific form of the body, 

 its regions and characteristic organs. The early stages in the 

 development, therefore, will receive but a scanty treatment here. 

 In the absence, however, of anything but the most fragmentary 

 records of the development of Corymorpha, it has seemed de- 

 sirable to include a few observations on its prelarval history. 



Although many naturalists have been more or less intimately 

 acquainted with CoryniorpJia since Sars described C. nutans in 

 1835, its young remained unknown until three larval stages of 

 the same species were described and figured by AUman ( :71). 

 These, including the sessile planula and polyps with six and six- 

 teen proximal tentacles, he supposed to have sprung from de- 

 tached rootlets, or frustules, instead of from eggs. The larva is 

 so different from the adult, and resembles so closely a diminutive 

 Tubi(IariaA\mt it was described recently by Hargitt ( :02) under 

 the name of T. parasitica. The misconception was pointed out 

 soon after in a letter to the American Naturalist (Torrey, :02a). 

 May ( :03) has published observations on the development of the 

 medusa and the ovarian egg. The only other references to the 

 subject are contained in two papers by the author ( :02 and : 04a) . 

 The former is a footnote, and the la' t n- considers verj^ briefly 

 the features of the development which are concerned with a study 

 of the behavior of the hydroid. 



II. — The Medusa, Eggs and Egg-laying. 



The medusa of C. palma (Figs. 1, 2), unlike those of the othei' 

 species of the genus, is probably never liberated from the parent 



