146 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



EXPLANATION OF THE PLATES. 



a, float ; h, nectocalyx ; c, necto-stem ; d, polyp-stem ; e, feeding polyp ; /, taster ; 

 g, ovaries ; h, testes ; 2, tentacle ; j, tentacular knob ; a, involucrum ; j3, sacculus ; 

 7, pedicel ; 5, terminal filaments ; Ar, tentacle of the taster ; Z, somatocyst ; n, radial 

 tubes ; o, circular vessel ; p, covering scale ; q, longitudinal canal ; ec, ectoderm ; 

 etiy entoderm ; r, joint in polyp-stem ; s, nectocalyx of diphyozoid ; t, crescentic- 

 formed velum in Gleba. 



The mantle-tubes, somatocyst, and central tube of the bract or covering scale are 

 designated by the letter I. They seem to be the same structures. 



PLATE I. 



Fig. 1, Apolemia uvariay a part of the polyp-stem, magnified four diameters. The 

 longest stem observed by me was eight feet in length. Figs. 2, 3, 4, 5, 6, 7, different 

 stages of development of the tentacular knob of Physophora hydrostatica. Fig. 3 

 shows the origin of the involucrum. Fig. 4, 5, 6, represents the provisional form of 

 the knob, and the embryonic terminal filaments. Fig. 7, a knob in the most developed 

 condition. 



PLATE II. 



Fig. 1, view of Agalmopsis pida from one side, magnified two diameters. The ten- 

 tacles are drawn to the vicinity of the polyp-stem by which the tentacular knobs 

 appear on the upper side of that appendage (an unusual condition.) Fig. 2, covering 

 scale of Agalma Sarsii. Fig. 3, portion of the polyp-stem of Halistemma rubrum, 

 magnified four diameters. Fig. 4, tentacular knob of Halistemma ruhrum. The 

 lower extremity of this figure joins figure 3 at the point y. Fig. 6, taster of Agal- 

 mopsis pida. This figure shows the position of the male and female organs in refer- 

 ence to the taster. 



PLATE III. 



Fig. 1, Praya diphyes. Fig. 2, Praya, sp. (?) This unknown species of Praya 

 differs from Praya cymhiformis in the equality in size of the nectocalyccs, their tri- 

 angular outline when seen in profile, and the direct course from junction to circular 

 vessel of the radial tubes. The difference between it and Praya diphyes is plainly 

 brought out by the accompanying Fig. 1. It has the somatocyst in but one necto- 

 calyx, and the diphyozoids are crowded together along the polyp-stem, somewhat 

 similar to the conditions among the Agalmidse. I incline to regard Fig. 2 as the 

 young of Praya cymhiformis. Fig. 3, Diphyes acuminata. Fig. 4, lateral view of 

 the nectocalyx of Gleba hippopus. Fig. 5, inferior view of a similar nectocalyx. 

 Fig. 6, Spheronedes {Monophyes) inermis. All these drawings are from Jelly-fishes 

 taken in the Mediterranean. 



