 Fig. 57. Hydrarium of Eucope; natural size. |  Fig. 58. Portion of Fig. 57; magnified. | |
 Fig. 59. Part of marginal tube and tentacles of Eucope, greatly magnified; e eye-speck, b base of tentacle., r reentering base of tentacle. |  Fig. 60. Young Eucope; magnified. | |
 Fig. 61. Adult Eucope seen in profile; magnified. |  Fig. 62. Quarter disk of Fig. 60, seen from below; e e tentacles bearing eye-speck. |
The tentacles are solid and stiff like little hairs, and two of them, in each quarter-segment of the disk, have small concretions at the base, which are no doubt eye-specks. (See [Fig. 62.]) Along the chymiferous tubes little swellings are developed, which increase gradually, and become either ovaries or spermaries, according to the sex of the animal. ([Fig. 63.]) In the adult the genital organs hang down, like elongated bags, from the chymiferous tubes. ([Fig. 64.]) The tentacles are numerous, multiplying to about a hundred and ninety-two in the adult, and increasing according to the numerical law to be explained in the description of the Oceania.
Fig. 63. Quarter-disk of young Eucope, older than Fig. 62, with a second set of tentacles (2) between the first set (1). | Fig. 64. Magnified quarter-disk of adult Eucope. |
This little Jelly-fish is one of the most common in our Bay. There is not a night or day when they cannot be taken in large numbers, from the early spring till late in the autumn; and as the breeding season lasts during the whole of that period, they are found in all possible stages of growth. In consequence of this, the course of their development, and the relation between the different phases of their existence as Hydroids, and afterwards as Acalephs, are well known, though the successive steps of their growth have not been traced connectedly, as in some of the other Jelly-fishes, the Tima or Melicertum, for instance. The process is, however, so similar throughout the class of Hydroids, that, having followed it from beginning to end in some of the groups, we have the key to the history of others, whose development has not been so fully traced. The eggs laid by the Eucope in the autumn develop into planulæ, which acquire their full size as Hydroid communities toward the close of the winter, and the development of the young Medusæ upon them, as described above, begins with the opening spring.
Oceania. (Oceania languida A. Ag.)
The Oceania ([Fig. 68]) is so delicate and unsubstantial, that with the naked eye one perceives it only by the more prominent outlines of its structure. We may see the outline of the disk, but not the disk itself; we may trace the four faint thread-like lines produced by the radiating tubes traversing the disk from the summit to the margin; and we may perceive, with far more distinctness, the four ovaries attached to these tubes near their base; we may see also the circular tube uniting the radiating tubes, and the tentacles hanging from it, and we can detect the edge of the filmy veil that fringes the margin of the disk. But the substance connecting all these organs is not to be distinguished from the element in which it floats, and the whole structure looks like a slight web of threads in the water, without our being able to discern by what means they are held together. Under the microscope, however, the invisible presently becomes visible, and we find that this Jelly-fish, like all others, has a solid gelatinous disk.