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Show 1903.] MEDUSA FROM BRITISH COLUMBIA AND ALASKA. 185 and sinks, with its tentacles fully expanded, until it reaches the bottom, or another piece of sea-weed where it attaches itself, and after remaining suspended a little while, repeats the same operation." Agassiz has emphasised this habit of turning over in the specific name vertens. This power of attachment is not, however, due, as Agassiz states, to the lasso-cells, but to a definite structure-an adhesive pad, an enlarged view of which is shown in PI. XXII. fig. 3, which is situated near the ends of the tentacles, and acts like a sucker, which is sufficiently strong to tear the tentacles without loosening its hold. This power of attachment must be of great service to the animal, for it prevents its being carried away by any struggling animal it may capture. It is quite probable this Medusa often captures animals fully as large as itself, as it readily tries to digest pfeces of meat, almost twice its size, which are dropped into the bell-jars in which they are kept during captivity. These Medusa? seem remarkably hardy and remain alive in small jars of sea-water without change of water for several days. 2. GONIONEMUS AGASSIZII, sp. nov. (Plate XXI. figs. 1, 2, & 3, and Plate X X I I . fig. 3.) Specific description.-The bell is 9 by 17 mm., or a little taller than a hemisphere. The subumbrellar surface dips down in the centre formimg a gastral cone. The velum is rather broad, strong, and well developed. The tentacles are shorter, more numerous than in any other species of this genus described. They number eighty in specimens of the above size. They are inserted into the bell-margin at different levels, giving the appearance of one row above another. In a moderately contracted condition they are not more than two-thirds the diameter of the bell in length. They are much thicker at the base, and taper more gradually towards the tips, than in any of the species already known. Each is provided with a small glandular attachment-pad some distance from the end (PI. X X I I . fig. 3). As already remarked, the proximal end of the tentacle is slightly enlarged just before entering the margin of the bell as in other species. This end of the tentacle is a tapering root connected with the circular canal. Just at the outer margin of the velum, under the circular canal, is a small ridge or welt of ectoderm filled with urticating-organs. It is reddish-brown in colour, the same as the papilla? below. There are papilla? under the circular canal on the bell-margin, just below the insertion of the tentacles, containing diverticula of this canal. Their outer layer is composed of the same tissue as that composing the nettle-ridge, and of a similar brown colour. There are not so many otocysts as tentacles, though there is no definite regularity. The pigment-spots at the bases of the tentacles are not visible in the preserved condition. |