MKDrs.E OF THE WORLD. 



of the mouth-part of the manubrium. Each one of these branches twice dichotomously, thus 

 giving rise to 4 tentacle tips in each quadrant. The gonads are found in the ectoderm of the 

 manubrium, where they occupy longitudinal, interradially situated, swollen regions. 



In the Tortugas and Charleston Harbor examples of this species, the entoderm of the 

 tentacle-bulbs and of the manubrium is of a delicate sage-green. The gonads are cream- 

 colored, and the tentacular ocelli dark-brown or black. In northern examples of this medusa, 

 found at Newport, Rhode Island, and Naushon, Massachusetts, according to A. Agassiz, the 

 tentacle-bulbs are colored with brilliant red, surrounded by a green edge bordered with bright- 

 yellow, and the digestive cavity is brick-red or green. No such brilliant coloration has been 

 observed by me in southern examples of this species. 



The hydroid stock has been figured by A. Agassiz, 1865, p. 158. It occurs very commonly 

 upon Fuciis vesifulosus, where it grows in dense clusters. The main stems are often 230 to 

 270 mm. in length. They taper gradually from base to summit and branch profusely and pin- 

 nately. The side branches do not often give rise to secondary branches. Great numbers ot 

 ringed pedicels, which terminate in polyp-heads, arise from the sides of the main stem and also 

 from the branches. The polypites are fusiform and possess a single circlet of about 15 long, 

 slender tentacles near the distal extremity. The mouth is situated at the apex of a slight, conical 

 proboscis. Medusa-buds make their appearance anywhere all over the stems, where they 

 appear either singly or in clusters. When set tree the young medusa is about 1 .7 mm. in height. 

 The bell is pyriform in outline, and the gelatinous substance quite thick. There are 8 tentacles, 

 2 at the base of each of the 4 radial tubes. The tentacles are all provided with basal ocelli. 

 The manubrium is small, slender, and tubular, and there are 4 short, unhranched, oral ten- 

 tacles. 



The general color of the stems of the hydroid is of a horny green and the polypites are 

 often of a delicate rosy tint. 



This medusa is very abundant throughout the summer in Charleston Harbor, South Car- 

 olina. It is much rarer at the Tortugas, Florida. The brilliantly colored, northern variety is 

 said to be quite common upon the southern coast of New England, but it has never been 

 found north of Cape Cod, Massachusetts. 



Hargitt, 1901 (Biol. Bulletin, Woods Hole, vol. 2, p. 228), discovered a remarkable twin 

 sport, apparently of this medusa. It had 2 manubria fused at a common base so as to form a 

 common stomach. Each "twin " had a complete bell-margin, only the sides ot their bells being 

 fused one to the other. 



Bougainvillia niobe Mayer. 

 Plate 18, figs. 1-3. 



Bougainvillia niohe, MAVF.R, 1894, Bull. Mus. Comp. Zool. at Harvard College, vol. 25, p. 236, plate I , fig. 2: Ifiiil., vol. 37, p. 42 ; 

 1904, Mern. Nat. Sd. Brooklyn Institute Museum, vol. i, p. 11, plate z, figs. 14-ijr. 



Adult medusa (plate i8,fig. I ). Bell 6.75 mm. high and 4.8 mm. in diameter, with vertical 

 sides and thick, gelatinous walls. 4 radially situated clusters ot marginal tentacles, each com- 

 posed of about 8 tentacles about as long as the bell-height. On the velar side of each tentacle, 

 near the bulbous base, there is a dark-colored ocellus. 4 straight, narrow radial-canals. 

 Manubrium wide, flask-shaped, and cruciform in cross-section. About half as long as the 

 height ot the bell-cavity. 4 radially situated clusters of oral tentacles, each of which branches 

 dichotomously 4 times. These are very flexible and their distal ends are knobbed. 



Medusa-buds arise from the 8 adradii of the manubrium, the youngest buds being im- 

 mediately under and on both sides of the point of entrance of each radial-canal, while older 

 ones are found farther down the sides of the stomach. The young buds are small, ovoid 

 vesicles contained entirely in the ectoderm. The limiting membrane, between the entoderm 

 and ectoderm of the manubrium in the neighborhood of these buds, is entire (plate 18, fig. 3), 

 and I can find no evidence of cells passing through it. Indeed, throughout the future develop- 

 ment of the buds, the entoderm remains inert and its limiting membrane unbroken. The 

 wall of the vesicle consists of 2 layers of cells: an outer epithelium of ectodermal cells, des- 

 tined to give rise to the ectoderm of the hud, and an inner layer of somewhat larger cells 

 destined to give rise to the entoderm of the budding medusa (plate 18, fig. 2). These latter 

 cells are entirely incased by the ectoderm of the parent. They may, however, have been 



