GEMMARIA CLADOPHORA. 



185 



but is curved in the opposite direction ; near the upper bend of the 

 chymiferous tubes, it runs up into a point, making a sharp and deep 

 groove round the projection of the 



Fig. 308. 



Fip. 30'J. 



spherosome; the chymiferous tubes 

 {c, Fig. 308), as well as the circu- 

 lar tube, are very broad (Fig. 308), 

 opening into a conical digestive 

 cavity, wliich at its base occupies 

 nearly the whole width of the up- 

 per part of the inner bell ; this cav- 

 ity tapers gradually till it reaches 

 the level of the veil, Avhere the 

 edges flare a little ; the extremity 

 of the proboscis has a tendency to be sliglitly drawn in, so that the 

 opening of the cavity is flanked by the pouches formed by the partial 

 contraction of a portion of the walls ; the walls are thick, and open into 

 a quadrangular mouth (Fig. 309), surrounded by a 

 cou])le of concentric rows of large la.^so-cells ; simi- 

 lar large cells extend on the outside of the chymif- 

 erous tubes, more than half-way up the sphero- 

 some. (Fig. 308.) 



The tentacles are broad and thick, two of them 

 ])eing more developed than the others (Fig. 307) ; 

 they are of a light-brown color, with orange pig- 

 ment-cells at the base ; the knobs of lasso-cells are attached to quite 

 long stems (Fig. 310) ; the walls of the digestive cavity are fi,. 310 

 thick ; the ovaries are placed in the upper part of the proboscis. 

 Found at Nahant in the beginning of August. When at rest, 

 the tentacles are stretched out very obliquely from the bell, 

 and they often remain perfectly motionless in this position ; 

 the Medusae are quite rapid in their movements. (Fig. 307.) 



Professor Clark discovered at Nahant a Hydroid closely resembling 

 the Coryne implexa of Alder, and which I suspect will prove to be the 

 nurse of our Gemmaria ; this would be in accordance with the observa- 

 tions of Allman on the development of Zanclea from Coryne imj^lexa. 

 Massachusetts Bay, Nahant (A. Agassiz). 

 Cat. No. 363, Nahant, 1862, A. Agassiz. Medusa. 

 ? Cat. No. 63, Nahant, May, 1862, H. J. Clark. Hydrarium. 

 Museum Diagram, No. 20, after A. Agassiz. 



Fig. 308. Quarter of the disk of G. cladophora, seen from the abaetinal pole. c. rironlar 

 tube ; c', chymiferous tube ; h, sensitive bulb, having a great accumulation of pigment and lasso 

 cells extending along the chymiferous tubes ; c", opening leading into the chymiferous tubes from 

 the digestive cavity, o : g, g, genital organs ; g', fatty globules at base of proboscis. 



Fig. 309. Actinostome of Gemmaria, enlarged. 



Fig. 310. Cluster of lasso-cells of the marginal tentacles. 

 NO. II. 24 



