Chap. I. ADULT MEDUSA OF CORYNE MIRABILIS. 215 



preventing, however, the food from escaping. After the nutritive fluid has made 

 its way into the central cavity, it is circulated into the radiating tubes, and 

 finally reaches the lower circular canal, moving to and fro in these canals, some- 

 times advancing from the centre towai-ds the periphery, at other times rising from 

 the periphery towards the centre, and flowing alternately one way or the other 

 in the circular tube. Tliere can be no doubt as to the irregularity of these 

 movements, as the granules suspended in the more liquid food may enable any 

 one, even with a low power, to trace the course of the nutritive fluid. 



The tentacles, also four in number, arise from the lower margin of the disk, 

 just at the point where the vertical chymiferous tubes unite with the circular 

 canal, and at these points there is a sort of bulb, consisting of the swelling of 

 the base of the tentacle in its connection with the chymiferous tubes, and also 

 of a jjeculiar accumulation of cells, forming a rudimentary visual apparatus in the 

 form of black eye-specks at the base of each tentacle. These tentacles are hollow, 

 and the liquid which circulates in the circular tube penetrates into their cavity, 

 up and down. They taper gradually, and are nearly cylindrical when extended, 

 but rather thick when contracted. There is not the slightest indication of an 

 aperture or jjuncture at their end, through which fluid might be absorbed, or refuse 

 matter from the chymiferous system rejected, nor is there any such opening in 

 any part of the circular tube, or of the other tubes through which the liquids 

 are circulated. The external surface of the tentacles appears rough, granular, or 

 rather tubercular ; and, when elongated, these tubercles are sufficiently distinct to 

 appear like rows of beads hanging loosely around a thread. But in their con- 

 tracted state they come so close together, that the whole surface of the tentacle 

 appears tubercular. Upon close examination, these tubercles are found to consist 

 of heaps of minute epithelial nettling cells, arranged in the form of rosettes or 

 mulberries, each of which contains within itself a thread coiled in a spiral, which 

 may be thrown out like the threads of all nettling cells, and is provided, at its 

 base, or at the vipper portion of the bulb formed by the cell, with a double hook. 

 See PI. XIX. Figs. 6 and 6^ and pages 208 and 209. 



The sensitive bulb, or eye, as I may well call it, is placed, as already men- 

 tioned, at the junction of the marginal tentacles and the circular and vertical tubes, 

 which pass into each other on their inner surface. It forms a marked projection, 

 and is of an irregular triangular form, with rounded edges (PI. XIX. Fig. 17). Seen 

 from below, it is divided into two halves bulging sideways, between which the 

 marginal tentacles arise. Seen in profile, the dark eye-speck appears still more 

 prominent, in the shape of a hemispherical body projecting above the base of the 

 tentacle. Seen from above and outside, it is more pear-shaped, the vertical tube 

 above each eye-speck appearing like a continuation of its upper end. The circular 



