396 Harry Beal Torrey. 



sexual origin of sexual individuals, and powers of movement that 

 are unusual for a hydroid. In the second place, very little is 

 known of its biology, and its value for experimental work has not 

 yet been generally realized. No account of its regeneration has 

 been published, with the exception of a brief reference to it in a 

 former paper by the present author ('02, p. 41). Up to this time 

 our knowledge of the egg-development has been based upon three 

 stages described and figured by Allman ('71):^ the sessile planula, 

 the polyp with six proximal tentacles, and the polyp with sixteen 

 to twenty. These Allman took for stages in the development of 

 what he called "frustules," minute bodies cut off from the pro- 

 cesses that develbp near the base of the stem and really give rise 

 to the filaments of the hold-fast. Had he seen the eggs on the 

 medusae in his aquarium, this pardonable error would not have 

 been made. Agassiz ('62) and Allman ('63) have given brief 

 accounts of the natural history of the hydroid and the develop- 

 ment of the medusa. 



These works, with several of a taxonomic character, and a 

 recent paper by May ('03), comprise the scant publications on 

 Corymorpha relating to the subject of this paper. 



I. DESCRIPTION OF C. PALMA. 



The nutritive polyps of C. palma are solitary. The stem may 

 reach the length of ten centimeters, tapering gradually from a 

 diameter of perhaps six millimeters, near the base, to a narrow 

 neck which supports the hydranth. It is covered for about its 

 proximal third with a thin, non-supporting layer of perisarc. 

 Within is a solid axis of immense vacuolated cells. These have 

 almost obliterated the cavity of the stem, which persists as a num- 

 ber of small, longitudinal canals lying immediately under the thin 

 mesogloea, and usually made conspicuous by their green tinted 

 walls. 



'A Monograph of the Gymnoblastic or Tubularian Hydroids. London, 1871. 

 The section in this magnificent monograph devoted to Corymorpha is a reprint of 

 Allman's paper in the Annals and Magazine of Natural History for January, 1863, 

 p. 1, with but slight verbal changes and the addition of figures. 



