of 

 of 



ii 



28 A DISCOLOURED SEA. [cha 



apparently different, species. Captain Cook, in his thl 

 voyage, remarks, that the sailors gave to this appearam 

 the name of sea-sawdust. 



Near Keeling Atoll, in the Indian Ocean, I observed many 

 little masses of confervae a few inches square, consisting of 

 long cylindrical threads of excessive thinness, so as to ~ 

 barely visible to the naked eye, mingled with other rath 

 larger bodies, finely conical at both ends. They vary 

 length from .04 to .06 and even to .08 of an inch In lengt 

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

 extremity of the cylindrical part a green septum, formed of 

 granular matter, and thickest in the middle, may general,' 

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

 colourless sac, composed of a pulpy substance, which lin 

 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 con- 

 tract 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, 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 exploding. 

 Their shape is oval, and contracted in the middle by a 

 ring of vibrating curved clllae. It was, however, very 

 difficult to examine them with care, for almost the Instant 

 motion ceased, even while crossing the field of vision, their 

 bodies burst. Sometimes both ends burst at once, sometimes 



