14 BAHIA BRAZIL. [CHAP, i, 



spaces in the Red Sea, and whence its name of Red Sea is derived.* 

 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 confervas They appear 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, 

 remarks, 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 confervas a few inches square, consisting of long cylin- 

 drical 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 brownish 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 contract itself, so that in the 

 course of a second the whole was united into a perfect little sphere, 

 which occupied the position of the septum at one end of the now 

 quite hollow case. The formation of the granular sphere was 

 hastened by any accidental injury. I may add, that frequently a 

 pair of these bodies were attached to each other, as represented 

 above, cone beside cone, at that end where the septum occurs. 



I will add here a few other observations connected with the 

 discoloration of the sea from organic causes. On the coast of 



* M. Montague, in Comptcs Rendus. etc., Jiiillet, 1844 ; and Annal. des 

 Scienc. Nat., Dec. 1841 



