78 MEDUSAE OF THE WORLD. 



DESCRIPTION OF AMERICAN SPECIMENS. 



Bell high with straight, vertical sides and flatly-rounded top, about 3 mm. high and 1.5 

 mm. wide. Bell-walls very thick and of a rigid, gelatinous consistency. Bell-cavity about 

 two-thirds as deep as the total height of the bell itself. There are 4 radially situated, slender 

 tentacles, all of the same length and not quite as long as the bell-height. Each ot these ten- 

 tacles terminates in 3 to 5 bulb-shaped, ring-like swellings containing nematocysts. The 

 basal bulbs of the tentacles are large and swollen, and each of them bears a dark-purple, 

 ectodermal ocellus upon its outer side. There are 4 straight, narrow radial-canals and a 

 simple, slender, circular vessel. The velum is quite narrow. The manubrium is a slender 

 tube about 5 mm. long; and it exhibits two separate, annular, swollen regions marking 

 the places where the gonads are situated. The mouth is a simple, round opening. The ento- 

 derm of the manubrium and of the tentacle-bulbs is of a beautiful custard-yellow, while the 

 entoderm of the terminal series of knobs on the tentacles is of a rich port-wine color. 



Several specimens were found in a surface-tow at Tortugas, Florida, early in August, 

 1898, and in July, 1906. 



DESCRIPTION OF EUROPEAN SPECIMENS. 



For details of the general characters of the European medusa, see tabular description 

 of the medusae of Slabberia. 



Forbes and Goodsir, 1853, describe this medusa from the western coast of Scotland, at 

 Tobermory and Loch Laigh. 



Keferstein, 1862, and Allman, 1871-72, describe that which I doubtfully believe to be 

 this medusa from the coasts of France and England. It is the immature condition before 

 the appearance of gonads, while medusa-buds are still being produced upon its manubrium, 

 and before the development of nettle-rings upon its tentacles. Chun, 1895, has made a most 

 careful study of this budding process in specimens from the Mediterranean. 



Haeckel, 1879, describes this medusa from the Mediterranean, but did not observe it 

 in the stage wherein medusa-buds are being produced. An identical medusa is found at 

 Tortugas, Florida. 



Chun, 1895, has made a careful study of the budding process. When the medusa^is 

 young the manubrium is slender and cylindrical and without gonads. Medusa-buds develop 

 at this stage. These budding medusae develop in a helical line at regular intervals down 

 the sides of the manubrium. The oldest of the primary series of medusa-buds is nearest the 

 base and the youngest nearest the mouth of the manubrium. 



These primary medusa-buds are attached by narrow pedicels to the sides of the manu- 

 brium, and a second series of medusa-buds develop upon the sides of these pedicels, before 

 the primary medusae are set free. After the primary medusae are set free the secondary medusa- 

 buds complete their development. Thus the manubrium may present various appearances; 

 the oldest medusa-buds at any one time may be above, or below, or anywhere upon the manu- 

 brium. Before they are set free the budding medusas begin to develop a secondary genera- 

 tion of medusa-buds upon their manubria. 



The hydroid of this medusa is described by Graeffe from Trieste, Adriatic Sea. GraefFe 

 succeeded in rearing the hydroid from the eggs of the medusa. It is a Syncoryne. The poly- 

 pites are cup-shaped, only 2 to 3 mm. long, and have 4 circlets of 4 tentacles each. The 

 tentacles are short and stiff, and each one ends in a nematocyst-knob. The short stems of 

 the hydroid are invested by an irregularly ringed perisarc. The hydrorhiza forms a mass of 

 profusely branched anastomosing stolons. The medusa-buds arise from the sides of the poly- 

 pites between the 2 lowest circlets of tentacles. When set free the medusa has a short man- 

 ubrium and 4 tentacles. The tentacles have terminal nematocyst-knobs and a nettling ring. 



The eggs are laid in May and June and the mature hydroid is found in October at Trieste. 



Chun is of the opinion that Sarsia clavata is identical with "D. dolic hogaster" ; but 

 Hartlaub regards S. clavata as being distinct and a true Sarsia. The absence of a series of 

 rings upon the tentacles of S. clavata inclines me to agree with Hartlaub that it is a Sarsia 

 and not to be confused with Slabberia catenata. Further studies appear to be required before 

 any final opinion can be formed upon this case. 



