SUMMARY OF RESULTS. 
1455 
In addition to the strictly bentlionic animals living attached to or creeping over 
the bottom, there are likewise in deep-water regions numerous Fishes, Crustaceans, and 
other organisms which live within about 100 fathoms of the bottom and occasionally rest 
upon it. These species are frequently taken in the trawls when this instrument has 
been dragged immediately over but not allowed to touch the mud or ooze covering the 
bed of the sea, and are also captured in the cages or traps let down into deep water. 
It has, however, been doubted whether the intervening waters in mid-ocean between one 
hundred fathoms above the bottom and a few hundred fathoms beneath the surface arc 
inhabited by marine organisms. The tow-net experiments carried out on board the 
Challenger during several years in all parts of the world led me to the conviction that 
these intermediate regions were inhabited, although with a much less abundant The Fauna oe 
fauna than the waters near the bottom or those near the surface of the ocean. Tf® I^'termedtat 
Thousands of hauls of the tow-nets were taken in the surface and sub-surface Ocean AVaters. 
waters, and the contents were daily submitted to microscopic examination ; the 
forms present in these waters became quite familiar to the naturalists. When, 
however, the tow-nets were sent down to deep water, and dragged in depths as 
nearly as possible of 500, 1000, and 2000 fathoms, organisms — such as the Tuscaroridm 
among the Radiolaria — were nearly always observed in the gatherings in addition 
to the usual surface organisms. Organisms from these intermediate layers of water 
appear to have a much wider horizontal distribution than the surface fauna or 
flora. These oft-repeated experiments produced a strong belief that all the 
intermediate zones of depth were inhabited. I am not aware that the Tuscaroridse 
have ever been taken in the surface or sub-surface waters. It is probable that the 
animals in the intermediate zones of depth obtain their food by the capture of the dead 
organisms continually falling from surface to bottom. It is well known that the deposits 
at the bottom are in most regions chiefly made up of the dead shells and skeletons of 
surface organisms. We have no definite ideas as to the rate at which these surface 
creatures may be falling to the bottom, but it is evident that nets which have been 
dragged in these intermediate depths on the opening and closing principle, without 
capturing any of these failing organisms, have either not been dragged for a sufficiently 
long time and through a sufficiently great extent of water, or have not worked 
successfully. 
The surface and sub-surface organisms are distributed in zones of latitude 
similar to the benthonic animals and plants of the shallow- water regions along the 
shore, but a very much greater number of the species are circum-tropical, circum-boreal, 
circum-antiboreal, and circum-polar. Species of Diatoms, Coccospheres, Rhabdosj)heres, 
Pyrocystis, Oscillariae, Protococcacese, Halosphsera, and the yellow cells of Radiolaria Pelagic Algaj. 
and Foraminifera together with other unicellular Algae, abound in the surface-waters 
