HALF AN HOUR WITH JELLY-FISH. 113 



are the Physalia, or " Portuguese Man-of-war," and 

 the Velella. The former is notorious for its intense 

 stinging powers, which surpass anything yet men- 

 tioned. Its long curled tentacles whip round an 

 object immediately, and, in the case of fishes, seem 

 to benumb them at once. Its shape is like that of 

 a spindle, tapering at each end, the numerous ten- 

 tacles trailing behind it as it swims. Usually it 

 makes its appearance on our coasts, not singly, but 

 in fleets. The Velella is nearly allied to the above, 

 although its shape is very different. Imagine a flat 

 disk, thin and somewhat cartilaginous, on which 

 another triangular disk is placed perpendicularly. 

 Its length is about two inches, and its height 

 one inch and a half. Its colour is fine blue, some- 

 times tinted with purple and green. When swim- 

 ming, or rather sailing, by the aid of the vertical 

 plate mentioned, which is acted upon by the wind, 

 it has somewhat of a rotatory motion. The Physalia 

 has no organ of locomotion whatever, but has to 

 trust to the mercy of winds, waves, and currents ; 

 the Velella being little better off in this respect, as 

 it only possesses its rudimentary sail. From the 

 under surface of the floating disk of the latter there 

 hangs down the polypite, and a series of marginal 

 tentacles. 



A much commoner and more thoroughly British 

 jelly-fish is the Beroe or Cydippe (Fig. 61), although, 

 singularly enough, it is structurally more nearly 

 allied to the sea-anemones than to the medusae. On 



