OCEANIA. 



53 



, 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 dis- 

 tinctness, 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 sub- 

 stance 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 mi- 

 croscope, however, the invisible presently becomes visible, and we 

 find that this Jelly-fish, like all others, has a solid gelatinous 

 disk. 



Let us begin with its earlier condition. When it first escapes 

 from the parent Hydroid stock, the Oceania is almost spherical 

 in form. (See Fig. 65.) The disk is divided by four chymiferous 

 tubes, running from the summit to the margin, where they meet 

 the cu'cular tube in which they all unite. At this time, it has 

 but two well-developed tentacles, opposite each other on the mar- 

 Fig. 66. 



gin of the disk, just at the base of two of the chymiferous tubes 

 (Fig. 66), while two others are just discernible in a rudimentary 



Fig. 65. Young Oceania just escaped from its reproductive calycle ; magnified. 

 Fig. 66. The same as Fig. 65, from below, still more magnified ; t long tentacles, t' rudimentary ten- 

 tacle, » eye-speck on each side of base of tentacles. 



