140 THE OCEAN WORLD. 



we find a great cavity, which opens from within, near the base of the 

 capsule ; to the inside of this cavity a second muscular sac is atttached 

 all round the opening of the capsule, in such a manner that the 

 opening leads directly into the cavity of the sac. This cavity conceals 

 in its interior a long filament usually rolled up in a spiral, as illus- 

 trated in Fig. 48, where the two urticating capsules of the stinging 

 apparatus of Physophora hydrostatka are represented, one of them 

 being a section, magnified by twelve diameters. This spirally 

 roUed-up filament consists of a large quantity of very small, hard, 

 sabre-shaped, corpuscular bodies, supported the one against the other, 

 and having their points turned inwards. These objects Vogt terms 

 "urticant sabres ;" the extremity of the filament consists of curved 

 corpuscles, larger, of a brownish yellow, very strong, and with ^ 

 double point. M. Vogt had also opportunities of observing the 

 action of these stinging capsules. He has seen them burst naturally, 

 and he has also obtained artificially the same result. In the former 

 case the filament issues from the opening left at the base of the 

 capsule with a sort of explosion. " The use," he says, " of the fishing- 

 lines becomes evident when we see a Physophora in repose in a vase 

 large enough for its full development ; then it takes a vertical position ; 

 the lines elongate themselves more and more, by unfolding one by 

 one the secondary lines with stinging capsules, and the Physophora 

 now resembles a flower posed upon a tuft of roots, with extremely 

 long and delicate rootlets reaching to the bottom of the vase. But in 

 the case of the Physophora the living roots are in continual motion. 

 Each line is elongated, foreshortened, and contracted in a thousand 

 ways. The least movement of the water causes the stinging capsules 

 to be suddenly drawn up, the lines hauled in most rapidly being those 

 near the crown of tentacles. This continuous play of the lines has 

 no other object than to attract the prey destined to feed the polyp, 

 and we cannot find any better comparison for them than the fishing- 

 lines to which they have been compared. The moment that some 

 small microscopical medusae, larva, or crustacean, come within the 

 sphere of those redoubted hues, it is at once surrounded, seized, and 

 led with irresistible force towards the mouth of this polyp by a gentle 

 and gradual contraction of the line ; the stinging organs, complicated 

 as we have seen them to be in the Physophora, thus serve the same 

 purpose as the stinging organs disposed on the arms of the Hydra, 

 or on the external surface of the tentacles and prolific polyps of the 

 Velella. 



Let us finally note among the Fhysalince — a family it will be 

 recollected of Physophoridce — a form which has attracted great 



