254 
THE VOYAGE OF H.M.S. CHALLENGER. 
fluxley,* clcep-sea clays and muds might be said to be of organic origin. In the 
Glol)igeriua limestones of Malta the tracks of Echinoderms and Annelids, which had 
eaten their way through the deposits, may now be seen in the solid rocks.* In 
examining the samples of Blue ]\Iuds, and especially those near the mouths of rivers, 
many oval-shaped bodies, about 0‘5 mm. in length, were observed. These were 
described by some observers as Foraminifera. Mr, Murray, after numerous observations, 
came to the conclusion that they were mostly the excreta of Echinoderms, principally of 
Holothurians.® When these pellets are voided by the animal they are covered by a 
slimy substance ; many of them may indeed be united in a chain. In some deposits this 
dung is exceedingly abundant, but as a rule it is imjDossible to recognise these oval bodies 
in any of the organic oozes, and in the Red Clays only some doubtful examples have been 
met w’ith. They appear to fall asunder when the deposit is granular, like a Globigerina 
Ooze, or when long exposed wdthout being covered up, as in the case of the Red Clays. 
It is abundantly evident, then, that much organic matter is mixed with the marine 
deposits, especially with the surface layers. In the Blue Muds the decomposition of 
this matter in the deeper layers leads to the reduction of the oxides in the red upper 
layer and to the formation of sulphides, which give a blue colour to the deposit, but in the 
Red Clays and Red Muds the quantity of organic matter is insufficient to completely 
effect this change, and the deposit as a whole remains of a red colour.* 
The changes connected with the decomposition of albuminoid matter in marine 
deposits must also be associated, at least in their initiatory stages, with the formation of 
glauconite in the chambers of Foraminifera and other calcareous organisms, and the 
production of glauconitic grains in Green and Blue Muds along continental shores. In 
like manner the formation of phosjjhatic grains and nodules may be connected with 
changes brought about by the decomposition of organic substances in terrigenous 
deposits. 
c. Changes Produced by Organisms in the Constitution of Sea-Water and Deep- 
Sea Deposits, 
When we remember the large number of marine organisms in the ocean, and the 
organic materials carried into the sea from the land, it is evident that the functional 
activity of these organisms, — together with the nitrogenous organic matter arising 
* .See p. 190. * Murray, Scot. Geogr. Mag., vol. vi. pp. 449-488, 1890. 
* .See under Additional Ol)servation8, pp. 101, 10.3. 
‘ J. Y, Buclianan Hays : — “Tlie mud Below the surface layer, in localities where ground life is abundant, remains 
blue, l»eing protected by the oxiilution of what is above it" (“ Sulphur in Marine Muds,” Proc. Roy. Soc. Edin., vol. xvii. 
p. 37, IStto). This does not ajjjjcar to be the correct interpretation, for Blue Muds, accumulating by additions at 
the 4urfaw, must all jwuw through the stage of the red upper or surface layer. The blue colour of the deeper layers must 
Ije due to a sulMe^iuent change from the reduction of the higher oxides in the red upper layer, and the formation of 
saipbide of iron through the decomposition of the organic matter present in the deeper parts of the deposit. 
