172 BULLETIN OF THE 



alone stretches over the terminal end of this organ. In this layer are epi- 

 theUan cells, modified into nervous elements. The otocyst is fastened to the 

 style, which bears it on the lower side, so that, instead of being continued, 

 directly into it, the cavity opens from the upper sides of the otocyst through 

 tho under side of the style. 



Exceptions to the regular number of otocysts in Cyanea and Aurelia are 

 common. 



Aurelia flavidula Pek. & Les. 



A few specimens of this medusa were taken each summer. They were as a 

 general thing fewer in number and smaller than those found in Massachusetts 

 Bay. An Aurelia as large as a water-bucket, which is not a rare sight north of 

 Cape Cod, I have not seen in the southern bays. A side view of a small Aure- 

 lia is beautifully figured in the well-knowTi " Contributions to the Natural 

 History of the United States." The figure is taken from a medusa with con- 

 tracted bell, and oral lobes, and consequently there is no representation in it 

 of the otocysts. I have given a figure of A urelia with disk expanded and oral 

 appendages extended, in order to show, more plainly than one in which these 

 parts are drawn together can, the position of the sense organs to which I 

 wish to call special attention. (Plate VII. fig. 2.) 



The otocysts of Aurelia differ very greatly from those of Cyanea, yet still we 

 can in both recognize homologous parts. The oral curtains hanging down 

 one on each side of the otocyst of Cyanea are wanting as such in Aurelia. They 

 are represented in part by two lappets, one on each side of the sense bulb, a, 

 Plate VII. fig. 3. Corresponding morphologically with the dendritic divisions 

 found in the oral curtains and adjoining sense lobes of Cyanea, there are in 

 Aurelia, arising as branches from the prolongation of the stomach into the 

 sense octant, two blindly ending horn-shaped tubes, which, as seen from above 

 (Plate VII. fig. 3, 6), appear to embrace the style of the otocyst, and extend a 

 short distance into the base of the lappets, a, Plate VII. fig. 3. The prolonga- 

 tion of the stomach into the sense octant, in Aurelia, takes the form of a 

 straight tube, the diameter of which is quite small. This tube, after arising 

 from the stomach, passes directly towards the margin of the disk, and when 

 near the otocyst opens into a circular-shaped enlargement. Into the same 

 cavity pass also two other pairs of chymiferous tubes, one on each side, which 

 are branches from another system of vessels likewise extensions of the stomach. 

 From the under floor of this ca\aty, which is shown in Plate VII. fig. 3*, near 

 its peripheral part, there arise three small vessels besides those which have 

 been already mentioned. One of these, the median, is continued directly into 

 the cavity of the otocyst, passing through the style of the same, while the others, 

 the two lateral branches, are the horn-shaped tubes which seem to embrace the 

 style of the otocyst, and enter for a short distance the lappets of the sense bulb. 

 Their extremities never become dendritic, but end blindly in the substance of 

 the lappet. As has been hinted at above, these sense lappets in Aurelia are 

 represented in part by the oral curtains hanging down, one on each side of the 



