746 PROCEEDINGS OF THE AMERICAN ACADEMY. 



section made below the level of the fu"st cut and near the lexe] of the 

 lower end of the stomodaeuin — but still through the anthocodiuni — 

 very close to the coenenchyma. The mesenterial filaments are cut in 

 this section. • The filaments belonging to the six ventral and lateral 

 mesenteries are very short (ne\'er more than two millimeters long, 

 and usually less than one), and appear as very slight thickenings of 

 the edge of each mesentery. The filaments of the two dorsal mesen- 

 teries are seen to be deeply grooved; they are very long and pass 

 with the mesentery from the stomodaeum to the Aery base of the 

 chamber, being much convoluted at their lower ends. The section 

 shown in Figure 4 is cut through the lowest part of the polyp cavity. 

 The Acntral and lateral mesenteries here have no filaments, but the 

 dorsal filaments, cut across several times, show their grooved condi- 

 tion. In the lower region of the polyp chamber are also many ova, 

 or else (the colonies being dioecious) masses of sperm mother cells 

 covered by the endoderm. The ova are attached singly to the sides 

 of the six ventral and lateral mesenteries. The eggs in July were 

 large, but there was no evidence of fertilized eggs or of matured sperm. 

 Phases in the retraction of the polyp have been described by Wright 

 and Studer ('89) and appear to be similar to those of Alcyonium 

 (Hickson, '95). When the colonies were transferred from the condi- 

 tions of the sea to those of the laboratorv, it was seldom that thev 

 remained as fully expanded as at first. The polyps were appreciably 

 shorter, but they had the shape and character described (Plate 1, 

 Fig. 1, a). Sometimes the mouth was open and observation showed 

 a slight current of water passing into the stomodaeum ; at other times, 

 or in other parts of the colony, the mouth was tightly closed. Some- 

 times the tentacles and pinnae were contracted to form eight short 

 cones at the top of a column comparatively well expanded, the mouth 

 being either open or closed. A circular constriction of a narrow region 

 then appeared just below the disk, while the remaining part of the 

 body bulged like a flask (Fig. 1, 7). A slow withdrawal of the polyp 

 then occurred, evidently by means of the longitudinal muscles of the 

 mesenteries, together with a slow inturning of the tentacles, until the 

 disk and tentacles were at the level of the calycle. These now drew 

 within and the oval or ovate calycle opening became visible (Fig. 1,5). 

 Sometimes in this method of contraction, the tentacles were first 

 rolled toward the mouth, giving the disk and tentacles the appearance 

 of a circle with eight indented radii (Fig. 1, (3). The column was then 

 contracted into the polyp ca^•ity of the coenenchyma, as already out- 

 lined. But this method of contraction is not the invariable rule. 



