DISCO LOKATION OF THE SEA FROM ALG.E. 19 



the colour of blood, and Captain Tuckey discovered that this 

 results from the reflection of the red ground-soil. 



But the essential colour of the sea undergoes much more 

 frequent changes over large spaces, from enormous masses of 

 minute algce, and countless hosts of small sea-worms, floating 

 or swimming on its surface. 



" A few days after leaving Bahia," says Mr. Darwin, " not far 

 from the Abrolhos islets, the whole surface of the water, as it 

 appeared under a weak lens, seemed as if covered by chipped 

 bits of hay with their ends jagged. Each bundle consisted of 

 from twenty to sixty filaments, divided at regular intervals by 

 transverse septa, containing a brownish-green flocculent matter. 

 The ship passed several bands of them, one of which was about 

 ten yards wide, and, judging from the mud-like colour of the 

 water, at least two and a half miles long. Similar masses of floating 

 vegetable matter are a very common appearance near Australia. 

 During two days preceding our arrival at the Keeling Islands, 

 I saw in many parts masses of flocculent matter of a brownish 

 green colour, floating in the ocean. They were from half to 

 three inches square; and consisted of two kinds of microscopical 

 confervas. Minute cylindrical bodies, conical at each extremity, 

 were involved in large numbers in a mass of fine threads." 



" On the coast of Chili," says the same author, " a few leagues 

 north of Conception, the ' Beagle ' one day passed through great 

 bands of muddy water ; and again, a degree south of Valparaiso, 

 the same appearance was still more extensive. Mr. Sulivan, 

 having drawn up some water in a glass, distinguished by the 

 aid of a lens moving points. The water was slightly stained, as 

 if by red dust, and after leaving it for sometime quiet, a cloud 

 collected at the bottom. With a slightly magnifying lens, small 

 hyaline points could be seen darting about with great rapidity, 

 and frequently exploding. Examined with a much higher 

 power, their shape was found to be oval, and contracted by a 

 ring round the middle, from which line curved little setae pro- 

 ceeded on all sides, and these were the organs of motion. Their 

 minuteness was such that they were individually quite invisible 

 to the naked eye, each covering a space equal only to the one- 

 thousandth of an inch, and their number was infinite, for the 

 smallest drop of water contained very many. In one day we 

 passed through two spaces of water thus stained, one of which 



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