]. r )0 



MEDUS.E OF THE WOULD. 



Stylactis hooped Sigerfoos. 



Xnlii'tn hooperi, SIUERFOOS, 1899, American Naturalist, vol. 33, p. 801, 5 figs. NuT-nun, 1901, Bull. U. S. Fish Commission 

 fur iS.j9, vol. ii), pp. 335, 374, figs. 13, 85. HAROITT, 1904, Bull. U. S. Bureau of Fisheries, vol. 24, p. 41. 



Medusa. The medusa is degenerate and intermediate in its character between the 

 sessile sporosacs of H \Jrtictinia and the well-developed, free-swimming medusae of Podo- 

 CDI via'. The medusae of Stylactis hooper I live only a few hours after being set free from the 

 hydroid, and die soon after setting free their genital products. The sexes are separate, the 

 mature genital products being developed within a large part of the ectoderm of the manu- 

 brium, so that the gonad encircles it as in the Codonidae. The evident relationship of the 

 hydroid to PoJocoryne, however, necessitates the medusa's being classified in connection with 

 Podocoryne, 



st- 



B 



Fi<;. 82. .S'/y/rtr/;s /joo/ipr/, after Sigerfoos, in American Naturalist. 



A. Colony shell of living llvanassa obsolete, represented as crawling over a blade of eelgrass. Natural size. 



B. Part of colony magnified 6 diameters, (i) large nutritive hydranth fully expanded ; (2) same slightly 



contracted; (3) same fully contracted; (4) large reproductive hydranth fully expanded; (5) smaller 

 reproductive hydranth, slightly contracted ; hr., tubes of hydrorhi/a ; sp., spines. 



C. Recently liberated female medusa, before extrusion of eggs, cc., circular canal; re., radial-canal; s/., 



Mnrnach; ;., tentacles ; z>., velum ; ov., ova. X 50. 



The bell is somewhat killer than a hemisphere, with thin, uniform walls. There are 8 

 short, marginal tentacles, 4 radial and 4 interradial. The velum is well developed. There 

 are 4 straight, slender radial-canals and a ring-canal. The manubrium is wide and spindle- 

 shaped and fills the greater part of the bell-cavity. There is no mouth-opening and there 

 are no oral tentacles. The ectoderm around the middle region of the manubrium is much 

 distended with the genital products. 



Hydroid. The hydroid was found by Sigerfoos growing upon the living shells of 

 Ilyanassa, especially upon snails found crawling upon eelgrass. It was found in Lloyds 

 Harbor, Huntington Bay, in Long Island Sound, New York, during the summers of 1898 99. 



