1879.] 295 [Fewkes. 
between this and the rapid motion of a Galeolaria, darting through 
the water almost with the velocity of a Doliolum, is very great. The 
lower Siphonophorae, as Physalia, have some means, passive as they 
are, of progression, but Rhizophysa seems to stand alone among the 
Siphonophorae in its helplessness. The animal, however, has a 
certain prehensile power in its polyps not unknown among other 
Siphonophores. Physophora hydrostatica, which manifests phenomena 
of sensation more quickly than the other Siphonophores, will grasp 
a pencil in its so-called tasters, and cling to it with great tenacity. 
That power is also, though in a less degree, possessed by the 
feeding polyps of Rhizophysa, The sensation however, in the whole 
body is very marked, as exhibited by the responsive contraction of 
the stem. When excited, the ability of the tentacles and their 
complicated tentacular knobs to grasp, is an additional element in 
the propulsive power of animals so helpless as Rhizophysa. Firmly 
seizing a floating weed, piece of wood, or even another living body 
(for I think at times even a large animal is fastened upon), it is thus 
moved from place to place by a foreign agent.t The Rhizophysa 
makes up in this way those means of progression of which it is 
destitute, but which even its own relations possess in such a highly 
developed form. .The peculiar problematical organs, which since 
Leuckart’s investigations have been commonly known as “ tasters,” 
are also wanting in Rhizophysa. ‘Three or four of those feeding 
polyps nearest the float, bear a very great resemblance to these 
structures in other Siphonophores. They have the same simple 
tentacles, and mouthless stomachs, but ure evidently only the unde- 
veloped stages of true feeding polyps. Farther down on the stem 
we find them passing into tentacles with tentacular knobs, and true 
polyps with mouths. 
The slender, needle-like shape of Rhizophysa, caused by its destitu- 
tion of swimming bells, renders it a most inconspicuous object in the 
water. The long tentacles hang gracefully down far below the 
extremity of the animal, at times contracting at the very base of 
1] have never seen it grasp the sides of a glass dish in which it was confined, and 
pull its float under water as Huxley says. Still the anastomosing tentacular knobs 
have the power of firmly fastening themselves to a foreign object, These struc- 
tures, however, it must be remembered, were not found in the species which 
Huxley had. Whenever I have found it attached, its whole body was coiled 
around the object very much in the manner in which it was found by Mr, Agassiz 
on the lines used by him in deep sea fishing, 
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