596 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 1 
among the Acraspedota. Some Medusew have partly or entirely given 
up the swimming mode of life, as Polyclonia, Cephea, and other Rhiz- 
ostoma, which lie with the back towards the sea bottom, the many- 
mouthed bunch of tentacles directed upwards. The Lucernaride have 
completely passed over to the benthos. Many Medusa are spanipelagie, 
rise to the surface only during a few months (for the purpose of reproduc- 
tion?), and pass the greater part of the year in the depths; thus in the 
Mediterranean the beautiful Cotylorrhiza tuberculata, Charybdea marsu- 
pialis, Tima flavilabris, and Olindias milleri. These bathybiec forms are 
sometimes brought upin great numbers with the bottom net (19, p. 122). 
Many cling with their tentacles to Alg@ and other objects (20, p. 341). - 
The immense swarms in which the Meduse sometimes appear, millions 
crowded thickly together, are known to all seafaring naturalists, 
Thus in Arctic waters, Codoniwm princeps, Hippocrene superciliaris; in 
the North Sea, Tiara pileata, Aglantha digitalis; in the Mediterranean, 
Liriantha mucronata, Rhopalonema velatum; in the tropics, Cyteis 
nigritina; mn the Antarctic Ocean, Hippocrene mocloviana and others. 
Hensen (9, p. 65) in the North Sea found a swarm of Aglantha, the 
number of which he estimated at twenty-three and one-half billions. 
The extent of the multitude was so great that “the thought of approxi- 
mately estimating the animals in this swarm must be given tp.” In 
such cases the whole sea for a few days, or even weeks, seems every- 
where fullof Meduse; and then again weeks, or even months, may pass 
without finding an individual. The wneertainty of appearance, the 
‘“‘ capriciousness of these brilliant beauties,” in cther words the depend- 
ence upon many different, and for the most part unknown causes, is i 
this interesting animal group remarkably impressed upon us. I will, 
therefore, in another place, refer to it on the ground of my own experience. 
Siphonophores.—W hat I have said above concerning the unequal dis- 
tribution of the meduse applies also to their wonderful descendants, 
the purely oceanic class of the siphonophores. This highly interest- 
ing class was, up to a few years ago, also regarded as purely pelagic; 
but of these, too, it is now known that they are in great part bathy- 
pelagic, in part also zonary and bathybic. The new and very peculiar 
group of the Awronecte (Stephalide and Rhodalide), taken by the Chal- 
lenger at a depth of 200 to 600 fathoms, is described in my ‘ Report of 
the Siphonophores of H. M.S. Challenger” (1888, p. 296). The Bathy- 
physa taken by Studer, and some of the Rhizophyside (Aurophysa, Lino- 
physa) captured by the Gazelle, were taken at a depth of 600 to 1,600 
fathoms (l.¢.). But that such deep-sea siphonophores (probably mostly — 
Rhizophyside) inhabited the ocean in great masses was first shown by 
Chierchia (8, p. 84-86). Previously, in numerous soundings which the 
Vettor Pisani had made in the Atlantic and Pacific oceans, the line of 
the deep-sea lead when drawn up was found to be wound around with 
the torn-off stinging tentacles of great siphonophores. By means of — 
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