136 Generation of Sulphur in 



of having been cast into elongated pellets. When these 

 were stirred up again with water they were partially broken 

 up into flocculent matter, which was poured off, leaving again 

 pellets as before; and this could be continued until the whole 

 of the mud had been washed away as flocculi, produced by the 

 breaking up of these pellets. In the case of the particular 

 mud under description, hardly anything in the shape of sand 

 or coarser material remained behind. The ground-fauna, 

 chiefly ophiurids, seemed to be abundant; and the pellets 

 above described were the casts excreted by these creatures, 

 which subsist on what nutriment they can pick up by triturating 

 and passing the sand or mud through their bodies. In some 

 of these animals the triturating apparatus takes formidable 

 proportions, as in sea-urchins; and it is probable that the 

 sand found at low water owes its state of comminution largely 

 to these animals and to worms, such as the ordinary lob-worm 

 used for bait. When examining deep-sea clays in the 

 "Challenger" I had observed the pellet formation, without, 

 however, being able to refer it to any probable cause. Now, 

 however, it became probable that the same causes are at work 

 in deep as in shallow seas, and that the matter forming the 

 bottom of the sea is being continually passed and re-passed 

 through the bodies of the numerous tribes of animals which 

 demonstrably subsist on the mud and its contents. 



In the following season, 1879, * made an extended cruise 

 through the greater part of the waters of the west coast of 

 Scotland, visiting most of the deeper spots, and paying particular 

 attention to the occurrence of coprolitic mouldings of the 

 mud. Thus, on i6th June 1879, dredging in the deep part 

 of the Sound of Raasay in 155 fathoms 1 , "a little mud came 

 up. It was a fine grey clay, which effervesced with acids 

 and smelled of H 2 S. On washing a quantity of it there remained 

 the coprolitic masses and very little fine sand. There appeared 

 to be a good deal of carbonate in a very fine state of division. 

 There were very few shell particles visible, and the effervescence 

 of what looked like flocculent clay was not inconsiderable." 

 At the time I explained this flocculent carbonate as having 

 1 From deck-book of steam yacht "Mallard," 1879. 



