The disk of the Discophoræ is by no means so delicate as that of the other Jelly-fishes. It seems indeed quite solid, and somewhat like cartilage to the touch, and yet so large a part of its bulk consists of water, that a Cyanea, weighing when alive about thirty-four pounds, being left to dry in the sun for some days, was found to have lost about 99/100 of its original weight,--only the merest film remaining on the paper upon which it had been laid. The prominence of the disk in this group of Jelly-fishes is well characterized by their German name, "Scheiben quallen," viz. disk-medusæ. We shall see hereafter that the disk, so large and seemingly solid in the Discophoræ, thins out in many of the other Jelly-fishes, and becomes exceedingly concave. This is especially the case in many of the Hydroid Medusæ, where it assumes a bell-shaped form, and is constantly spoken of as the bell. It should be remembered, however, in reading descriptions of these animals, that the so-called bell is only a modified disk, and perfectly homologous with that organ in the Discophoræ. The Discophorous Medusæ are distinguished from all others by the peculiar nature of the reproductive organs. They are contained in pouches (Fig. 50, _o_, _o_, _o_, _o_), the contents of which are first discharged into the main cavity, and then pass out through the mouth. Pillars support the four angles of the digestive cavity, thus separating the lower from the upper floor of the disk, while the chymiferous tubes (Fig. 50) branch and run into each other near the periphery, forming a more or less complicated anastomosing network, instead of a simple circular tube, as is the case with the Hydroid Medusæ. (Fig. 74.) _Cyanea_. (_Cyanea arctica_ PÉR. et LES.)