Flints of the Upper or White Chalk. 203 



bed, which would settle and develop wherever there were 

 vacant areas and favourable conditions. In those tracts 

 where the sponge-fields were altogether predominant, the 

 dense colloidal areas, viscid and coherent enough to pre- 

 vent their flowing out laterally, would become consolidated 

 into tabular sheets, more or less unbroken, inasmuch as their 

 contractility would exert itself chiefly in decreasing their 

 thickness, as the expulsion of the combined water would go 

 on uninterruptedly over their entire surfaces. On the other 

 hand, in those tracts in which Sponge and Foraminiferal 

 life had been split up into small contiguous patches, or the 

 sponges occupied only sparsely scattered plots, the nodular 

 flints would form, and be correspondingly distributed through 

 the calcareous bed. It is here that the powerful contractile 

 power resident in the colloidal masses would exert itself most 

 freely on all sides, every little irregularity of surface caused 

 by living or dead animal structures &c. tending still further 

 to break up the masses, which, during their tearing asunder, 

 would assume the amcebiform outlines which have been so often 

 referred to by me as specially characteristic of animal proto- 

 plasm or albumen, and which may, to a certain extent, be seen 

 when fresh albumen is mixed with cold water and gently 

 shaken up, and then allowed to settle. That protoplasm — the 

 protoplasm of the deep-sea sponges — does veritably assume 

 these forms is an indisputable fact, attested by Hackel and 

 Sir Wyville Thomson. I had myself once seen this material 

 00° the south-east coast of Greenland, in a sounding taken at a 

 depth of nearly a couple of thousand fathoms, in which I found 

 the minute sponge which Mr. Perceval Wright named after 

 me. But I had not any idea at the time, or until many 

 years afterwards, what the extraordinary glairy substance 

 pervading the mud really was ; and consequently I threw 

 away the only chance I have had of seeing it in its perfectly 

 recent stage. 



It is a remarkable circumstance that, throughout the long 

 cruise of the ' Challenger," nothing whatever should have been 

 discovered which might throw some light on the formation of 

 the flints at the sea-bottom. Constant mention has been 

 made of the immense abundance, in certain regions, of 

 sponges ; but I am not aware that any dead shell of a mol- 

 lusk or echinoderm was found in the dredgings, the interior of 

 which was filled up with colloid silica, or silica in an already 

 consolidated state. One would have thought that, amongst 

 the almost countless number of shells landed on the deck of 

 the ship, whether from calcareous or siliceous bottoms, some 

 trace of incipient fossilization or flint-formation must have 



