THE VOYAGE OF THE BEAGLE 25 



weak lens, seemed as if covered by chopped bits of hay, with 

 their ends jagged. These are minute cylindrical confervae, 

 in bundles or rafts of from twenty to sixty in each. Mr. 

 Berkeley informs me that they are the same species (Tricho- 

 desmium erythraeum) with that found over large spaces in 

 the Red Sea, and whence its name of Red Sea is derived. 8 

 Their numbers must be infinite : the ship passed through 

 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. In almost every long 

 voyage some account is given of these confervae. They ap- 

 pear especially common in the sea near Australia; and off 

 Cape Leeuwin I found an allied but smaller and apparently 

 different species. Captain Cook, in his third voyage, re- 

 marks, that the sailors gave to this appearance the name of 

 sea-sawdust. 



Near Keeling Atoll, in the Indian Ocean, I observed 

 many little masses of confervae a few inches square, consist- 

 ing of long cylindrical threads of excessive thinness, so as 

 to be barely visible to the naked eye, mingled with other 

 rather larger bodies, finely conical at both ends. Two of 

 these are shown in the woodcut united together. They vary 

 in length from .04 to .06, and even to .08 of an inch in 

 length ; and in diameter from .006 to .008 of an inch. Near 

 one extremity of the cylindrical part, a green septum, formed 

 of granular matter, and thickest in the middle, may generally 

 be seen. This, I believe, is the bottom of a most delicate, 

 colourless sac, composed of a pulpy substance, which lines 

 the exterior case, but does not extend within the extreme 

 conical points. In some specimens, 

 small but perfect spheres of brown- 

 ish granular matter supplied the 

 places of the septa; and I observed the curious process by 

 which they were produced. The pulpy matter of the internal 

 coating suddenly grouped itself into lines, some of which 

 assumed a form radiating from a common centre; it then 

 continued, with an irregular and rapid movement, to con- 

 tract itself, so that in the course of a second the whole was 



* M. Montagne, in Comptes Rendus, etc., Juillet, 1844; and Annal. des 

 Scienc. Nat., Dec. 1844. 



