THE IMPENETRABLE SEA 



Several years before this, Dr. E. H. H. Old, in the 

 Philippine Journal of Science^ reported the death of a boy 

 of fourteen, who was stung by a man-of-war and died 

 in a state of hysteria. 



There are many other jelly-fish which are harmful, and 

 some of these resemble the man-of-war, although none 

 possess all its fighting and sailing qualities. There is, for 

 instance, the Velella jelly-fish, which is very abundant in 

 tropical waters, and may often be found washed up in 

 its thousands on the Florida beaches. It is sometimes 

 confused with the man-of-war, for it also has a raft- 

 like float, but it is quite distinct in shape, being long and 

 flattened, while it is vividly blue in colour. 



Apart from the fact that both the man-of-war and the 

 Velella have floats there is little resemblance between 

 them. The man-of-war's tentacles, as we have seen, are 

 capable of extension to fifty feet, but the Velella' s are short 

 and thread-like, while the animal (or "polyperson", to 

 use its more accurate name) has a "hull" which is 

 divided into watertight compartments, which is an ad- 

 vance on the man-of-war's one-compartment structure. 

 Another striking diflference is that the Velella has a well- 

 developed triangular sail placed diagonally across it. 



Despite the fact that the Velella is an abundant and 

 widespread polyperson, scientists know little about it. 

 Yet from the time of Haeckel, who studied the Hydro- 

 medusae exhaustively, an enormous amount of human re- 

 search has gone into the investigation of the anatomy and 

 habits of this group of marine animals. There are vast 

 varieties of them, and even the single order of Siphon- 

 ophora, to which the man-of-war and Velella belong, has 

 so many diflferentiated kinds, some of which merge into 

 each other, while numbers of them present problems of 

 classification, that scientists cannot agree among them- 

 selves in their theories regarding the life-cycles and 

 anatomical devices of numerous members of the group. 

 Many jelly-fishes, in fact, which are much simpler in 



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