EQUIPMENT. 



35 



fine gauze, or of a net of similar niaterial (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 Muller, Pourtales, 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. '^' " ' "" ^°°^'^ ®*' 

 The naturaHsts of the " Challenger " attempted to prove 

 during her cruise that some of these forms lived at great depths, 

 and that there was practically no belt of ocean entirely barren 



Fig-. ;32. — 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 



