8 Cruise of the "Alert" 



called the Sargasso Sea. It was encrusted with a delicate white 

 Polyzoon (Membranipora), and among other organisms carried on 

 its fronds a pretty little Spirorbis shell, and several entomostracous 

 Crustaceans of a deep-blue colour. 



The phosphorescence of the sea is a trite subject, and one about 

 which a very great deal has been written ; but nevertheless, of its 

 actual cause, or of the purposes which it is intended to serve, really 

 very little is positively known. The animals to which it would 

 seem mainly due are the small stalk-eyed Crustacea, the Pyrocystis 

 noctiluca, and the Tunicate Molluscs. I have sometimes observed, 

 when occupied at night in sifting the contents of a tow-net, that 

 these organisms, as they were being sucked through the nozzle of 

 the dip-tube, emitted flashes of light, so brilliant, that they could 

 be distinctly seen even in a well-lighted room. During the voyage 

 from England to Madeira, the wake of the ship was every night, 

 with one exception, phosphorescent. The exception alluded to 

 was on the night previous to our arrival at Madeira, when pro- 

 bably the unusual brilliancy of the moonlight caused the light- 

 emitting creatures to retreat a few yards from the surface, as 

 happens in the day-time. I have often noticed that while the 

 phosphorescence of the comparatively still water abeam of the 

 ship and on her quarter usually seems to emanate from large 

 spherical masses of about a foot in diameter (commonly called 

 "globes of fire"), yet the luminosity of the broken water in the 

 vessel's immediate wake comes apparently from innumerable minute 

 points. I have rarely captured any of the larger jellyfishes in 

 the tow-net ; and on those nights when I have observed the water 

 lighted up the most brilliantly, the prevailing organisms have proved 

 to be the small entomostracous Crustaceans. 



The morning of the 7th of October broke cool and hazy, as we 

 steamed up and dropped anchor in Funchal Roads, on the south 

 side of the island of Madeira. Crowds of native boats, with 

 their half-naked occupants, quickly thronged around ; remaining, 

 however, at a respectful distance, until the boat containing the 



