1885-S6.] Edinburgh Naturalists' Field Chib. 277 



at sunset they sank, and it was suggested that the evohition of 

 gas might have something to do with the movement.^ 



As a result of a chemical examination of meteoric masses carried 

 out by Zimmermann in 1821, after an appearance of blood-rain, the 

 coloration was ascribed to a peculiar substance of doubtful nature, 

 which was named Pyrrhin. The importance of the red colour 

 produced by adding silver nitrate to amber containing organic 

 matter was also jDointed out by physicists ; while Hermbstadt and 

 Berzelius were inclined to recognise the existence of a transitory 

 substance in sea-water, produced by the decomposition of organic 

 bodies. Witting,^ on the other hand, regarded the redness to be 

 the result of the union of carbo-hydrates with water. 



To G. von Esenbeck the somewhat poetical idea held by some, 

 that in the atmosphere a workshop of living forms was to be met 

 with, appeared trivial ; while the operation of certain physical factors 

 referred to by others was to be kept under due bounds. All the 

 blood-like appearances were to be looked upon as due to siliceous 

 earth, or even oxide, or to grains of pyroxene and augite. 



F. von Esenbeck, brother of the observer last noted, again re- 

 cognised the part played by infusoria in producing the red colour of 

 water, and the organism believed to be the direct cause was named 

 Enchehjs sanguinea. Its colour was due to the presence of an in- 

 ternal, brownish-red, granular mass ; the ends of its body were 

 transparent, the anterior being truncated and the posterior pointed. 



Ehrenberg now recorded the effect produced by Oscillatoria 

 major, or a nearly allied species, in colouring water ; while Bory 

 sometimes observed, by aid of the microscope, a circulation of the 

 colouring matter in the filaments. At (Jairo, in Egypt, Ehrenberg, 

 in 1823, found red spots which he ascribed to a fungus, Sarcoderma 

 sanguineum ; while the small fungus, Geocharis iiilotica, was also found 

 in a highly coloured condition on the banks of the Nile. At Siut, 

 in Upper Egypt, in 1821, stagnatit water was found to be coloured 

 red by SpJueroplea anmdina, Ag. While in 1823, the Eed Sea, 

 near Tor, was tinged by, for the most part, dark-red organisms, 

 which proved to be OscillatoricB enclosed in mucilage, and wei-e 

 named Trichodesmkun erythrceum. Again, in Siberia, in 1829, Ehren- 

 berg found a marsh coloured red by the presence of an infusor, 

 Cercaria vlridis (Miiller). 



In the sea, especially in tropical or subtroisical localities, the 

 existence in clear blue water of streaks of green or brownish-red 

 colour occurring in the same locality are not unfrequent. The 

 existence of floating masses of living Diatoms esijecially bring 

 about this aijpearance — e.g., Rhizosolenia^, Cha?tocerotida^, and 



^ 'Mem. de la Soc. de Phys. et d'Hist. nat. Geneve,' vol. iii. p. 30; 

 Ehi-enberg in ' Poggend. Ann d. Phys. et Chemie,' p. 130. 



2 ' Archiv. d. Apothek. Vereins in nordl. Deutschl.,' Bd. ix., p. 215. 



