90 Dr. Colli ngwood, on Microscopic Alga. 



trical beauty of the filaments when taken fresh from the ocean, 

 and I can only suppose that Montague's specimens, obtained 

 upon a piece of linen by M. Dupont, had become, in drying, 

 so altered in form that subsequent moistening failed to render 

 them recognisable. 



The echiniform body (fig. g), which I consider to be an 

 Oscillatoria, was surrounded by a gelatinous envelope, and 

 was hard and dense in the centre, and therefore opaque On 

 applying gentle j)ressure, the villous appearance was shown 

 to be due to the free ends of a great number of filaments 

 which intermix with one another in the mass, and formed a 

 minute solid ball. They were unbranched, but twisted around 

 one another, and agglutinated together in a complex manner. 

 While thus engaged in examining them, the filaments one 

 after another suddenly broke up, the little masses of con- 

 tained endochrome separating from one another, not retaining 

 each its cell-form, as in the case of the Confervse just de- 

 scribed, but rapidly vanishing under my eyes in a smoke-like 

 manner, until, at the expiration of five or six minutes, there 

 was nothing left of the whole ball but a general granular and 

 amorphous appearance. 



A species of Trichodesmium was met with by Dr. Hinds, 

 H.M.S. Sulphur, in 1826, on the west coast of North America, 

 and again, in 1837, near St. Salvador, and was referred by 

 Mr. Berkeley to M. Montague, who regarded it as a new 

 species, and named it T. Hindsii. This species, he says, w'as 

 like that of the Arabian Gulf (which has been called T. 

 Ehrenbergii) , of a fine red colour, and was further remark- 

 able for the strong musty odour which it gave out, and which 

 deserved the name of olidum. But as I have, on the one 

 hand, remarked that I have nowhere met with Trichodesmium 

 of a red colour, but always of the same fulvous or dirty 

 yellow, so also I must add that on no occasion have I observed 

 any peculiar smell, even when it has been thickest, nor have 

 I ever heard any one with more acute perception of odour 

 than myself rem. ark anything unusual of that nature. 



M. Ehrenberg, in the original article in ' Poggendorf's 

 Annalen,' states that it was not a permanent phenomenon in 

 the Red Sea, but having observed it three times, viz., on the 

 25th and 30th December, and 5th January, he suggests a 

 periodicity. The appearance and disappearance of the Alga, 

 other things remaining the same, seems to me to be more re- 

 markable than its permanence Avould have been, but I have no 

 reason to believe that it is in any way a periodic phenomenon 

 in the China Sea, for at any day, on successive days, and at all 

 seasons, I have observed it unchanged. Ehrenberg's speci- 



