138 



MF.ni'S.K OF THK WORLD. 



there is no trace of interradial tentacles at the time when the medusa is liberated. The manu- 

 hrium is short and fusiform and the mouth is surrounded by 4 radially situated, oral tentacles, 

 each of which terminates in a knob-shaped cluster of nematocysts. When set free the medusa 

 is about 0.5 to 0.6 mm. in height. 



In those medusae which are set free in an immature condition there are at first 8 tentacles, 

 but these increase in number as growth proceeds and finally, when the medusa is about 3.5 mm. 

 in height, there are usually about 32 tentacles, 8 in each quadrant. The manubrium of the 

 young," immature medusa is slender and fusiform, while in those medusae which are set free in a 



I'u.. 74. / 



c 



- tii'iii-ii, livdroid ami young medusa. Drawn from lift" by Professor William K. Brooks 

 and kindly presented to the author for publication in this work. 



mature state it is globular and greatly distended with the genital products. The ectoderm of 

 the hydroid is slightly bluish and translucent, while the entoderm is creamy-pink, or silvery- 

 white in color. 



This species has been found upon the Atlantic coasts ot Europe, in the Mediterranean 

 Sea, and trom Saldanha Bay, Cape Colony, South Africa. Levinsen, 1893, records it from the 

 west coast of Greenland, and we have found it in great abundance in Narraganseit and 

 Buzzard's Bays, on the southern coast of New England. It has not been taken at Beaufort, 

 North Carolina, nor at any station farther south. The medusae are very common in Narra- 

 gansett Bay from the middle of June until October, and I enjoyed exceptional opportunities 



