1832.] PELAGIC CONFERVE AND INFUSORIA. 15 
o 
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 confervee a few inches square, consisting 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 —_tS> 
-04 to -06, and even to ‘08 of an 
inch in length; and in diameter from ‘006 to ‘008 of a 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 deli- 
cate, colourless sae, 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 for- 
mation 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 here add a few other observations connected with the 
discoloration of the sea from organic causes. On the coast of 
Chile, a few leagues north of Concepcion, the Beagle one day 
passed through great bands of muddy water, exactly like that of 
a swollen river; and again, a degree south of Valparaiso, when 
fifty miles from the land, the same appearance was still more 
extensive. Some of the water placed in a glass was of a pale 
reddish tint; and, examined under a microscope, was seen to 
swarm with minute animalcula darting about, and often explod- 
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