JELLY-FISH, ETC. 



483 



relates that during the first voyage round the world made by the ship Princess 

 Louise, a sailor jumped into the sea to capture a large Physalia. As he seized it, 

 the animal enveloped him in its long filaments, stinging him so terribly that he 

 cried out for help, and was hardly able to swim back to the ship to let himself be 

 hoisted up. Severe inflammation and fever followed, and his life was for some 

 time despaired of. 



During the Challenger expedition, deep-sea Siphonophora of a remarkable 

 kind were brought to light. The most interesting belonged to a new family, the 

 Auronectidce. The colony, instead of being a long string of individuals, is here 

 thickened and shortened so as to be oval or round. It consists of a hard, 

 cartilaginous mass, traversed by a close system of branching canals. The upper 

 part of this mass is a large, round, hollow air-bladder (p in the figure). This 

 pneumatophore is surrounded by a 

 circle of large, round swimming-bells 

 (n), one of which (?) is modified in 

 a remarkable way. It is not, like 

 the rest, quite hollow, but is traversed 

 by a narrow canal attached to its 

 walls by strands of gelatinous tissue. 

 The free end of the canal opens out- 

 ward through a short tube, while its 

 attached end enters the great 

 bladder of the pneumatophore. This 

 specially modified rowing-bell has 

 been called the aurophore, since it 

 appears to regulate the quantity of 

 air in the air-bladder. In order to 

 sink to a greater depth, the Stephalia 

 has only to contract its pneumato- 

 phore, discharging the air through 

 the lateral canal. When the animal 

 rises, the aurophore probably secretes a gas which fills the pneumatophore again. 

 The lower end of the colony is occupied by a large feeding or nutritive polyp, 

 and at its sides there are several rows of smaller nutritive polyps (s), each of 

 which, at its base, carries a capturing filament (t), and at its side grape -like 

 clusters of reproductive bodies. 



The Siphonophora, as a rule, require frequent changes of depth. It does not 

 appear that exclusively deep-sea forms are to be found in the Mediterranean, but 

 that all Siphonophora under certain circumstances and at certain seasons appear 

 at the surface. Many pass through their larval development at a great depth, 

 and the young Pltysopliora larvae found at the surface in the spring descend to 

 greater depths at the commencement of summer, and only return, when their 

 metamorphoses are complete, to develop into sexually mature animals. In the 

 Pliysophoriditi we had the different individuals in a long series. In the A uronectidce 

 we found them arranged in a compact mass; and, lastly, in the Velellidce, the 

 body is flattened out to a disc, which is traversed by a system of canals. On 



Stej^ha/ia (nat..size) 



