EQUIPMENT. 35 
fine gauze, or of a net of similar material (Fig. 32), towed be- 
hind a boat moving quite slowly. At the least ripple of wind 
they retreat out of reach of the disturbance, and occupy a belt 
of water probably one hundred, or at the outside one hundred 
and fifty fathoms in depth. When they die their shells or hard 
parts slowly find their way to the bottom, to serve, before they 
are completely decomposed, as food for the deep-water forms. 
The shells of many foraminifera and the like 
being found apparently in such a fresh state at 
the bottom, it was supposed that many of these 
pelagic forms only came up accidentally, and 
really lived at or near the bottom. This seemed 
the more probable because there are undoubt- 
edly many types of foraminifera which are 
inhabitants of deep water. Still, the investiga- 
tions of Miiller, Pourtalés, Schultze, Haeckel, 
and of all the naturalists accustomed to the 
study of pelagic forms plainly showed that a 
great number of the types of which the dead 
remains were found on the bottom really passed | 
their existence as pelagic forms near the sur- 
face, within a comparatively narrow belt, where \ 
they could find the greatest abundance of food. ашу е ant Cr 
The naturalists of the “ Challenger” attempted to prove 
during her cruise that some of these forms lived at great depths, 
and that there was practically по belt of ocean entirely barren 
2, — Tow-Net. 
of animal life. The means adopted on the “Challenger” to 
solve the problem did not, however, settle the point definitely. 
The old practice was employed of dragging for animal forms at 
intermediate depths by means of a tow-net, which, during the 
