290 PROGRESS or MICROSCOPICAL SCIENCE. 
shortly after the ‘ red clay ’ has assumed its most characteristic form, 
bv the removal of the calcareous matter of the shells of the Forami- 
nifera, at a depth of say 3000 fathoms, the deposit begins gradually to 
alter again by the increasing proportion of the tests of Radiolarians, 
until, at such extreme depths as that of the sounding of the 23rd of 
March, it has once more assumed the character of au almost purely 
organic formation, the shells of which it is mainly composed being 
however in this case silicious, while in the former they were cal- 
careous. The ‘ Radiolarian ooze,’ although consisting chiefly of the 
tests of Eadiolarians, contains, even in its present condition, a very 
considerable proportion of red clay. I believe that the explanation of 
this change, which was suggested by Murray, and was indeed almost 
a necessary sequence to his investigations, is the true one. We have 
every reason to believe, from a series of observations, as yet very 
incomplete, which have been made with the tow-net at different depths, 
that Radiolarians exist at all depths in the water of the ocean, while 
Foraminifera are confined to a comparatively superficial belt. At 
the surface and a little below it the tow-net yields certain species ; 
when sunk to greater depths, additional species are constantly found, 
and in the deposits at the bottom new forms occur, which are met 
with neither at the surface nor at intermediate depths. It would 
seem also that the species increase iu number, and that the individuals 
are of larger size as the depth becomes greater; but many more 
observations are required before this can be stated with certainty. 
Now, if the belt of Foraminifera which, by their decomposition, 
according to our view, yield the ‘ red clay,’ be restricted and constant 
in thickness, and if the Radiolaria live from the surface to the bottom, 
it is clear that, if the depth be enormously increased, the accumulation 
of the Radiolarian tests must gain upon that of the ‘ red clay,’ and 
finally swamp and mask it.” Professor Wyville Thomson further 
informs me that the best efforts of the £ Challenger’s ’ staff have failed 
to discover Batliybius in a fresh state, and that it is seriously sus- 
pected that the thing to which I gave that name is little more than 
sulphate of lime, precipitated in a flocculent state from the sea water 
by the strong alcohol in which the specimens of the deep-sea sound- 
ings which I examined were preserved. “ The strange thing is, that 
this inorganic precipitated is scarcely to be distinguished from pre- 
cipitated albumen, and it resembles, perhaps even more closely, the 
proligerous pellicle on the surface of a putrescent infusion (except in 
the absence of all moving particles), colouring irregularly but very 
fully with carmine, running into patches with defined edges, and in 
every way comporting itself like an organic thing.” Professor 
Thomson speaks very guardedly, and does not consider the fate of 
Bathybius to be as yet absolutely decided. But since I am mainly 
responsible for the mistake, if it be one, of introducing this singular 
substance into the list of living things, I think I shall err on the right 
side in attaching even greater weight than he does to the view which 
he suggests. 
