1832.1 PELAGIC CONFERVA AND INFUSORIA. 15 



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 conferva9 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 ^.^ir:r^---^^:;|---^ ^ 



together. They vary in length from ^- ^»^ """'""""'""'''"" ^'^> '^^ 



•04 to '06, and even to "OS 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 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 tlie whole was 

 united into a perfect little sphere, w^iiich 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 orofanic 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- 



