OBSERVATIONS WANTED 195 



specimens of any species under study ; thus it can be 

 readily shown in accurate terms that a species is rare 

 at the one hour, depth, date, or place, and common at 

 the other. Every haul made for comparative work 

 (and that is pre-eminently the work now required) 

 should be made with standard nets, time, and speed. 

 The only thing difficult of control is the speed, except 

 in a small launch, but this can be read by a current 

 meter (p. 53-57). Standards are suggested on p. 199. 



As a rule, the greater number of the species captured 

 at or near the surface at any particular position at sea 

 will be found to extend to about 100 fathoms at that 

 position (not necessarily elsewhere, where the tempera- 

 ture and other conditions may be different). For a 

 proper study of the alleged up-and-down movements 

 of the Plankton, and for many similar objects, it is 

 desirable to know, not only whether it is rarer or more 

 abundant at the surface under certain circumstances, 

 but also where it goes to when not at the surface. 

 The method of hauls with open nets at various depths 

 (p. 190) will throw a good deal of light on this, but 

 they are not to be trusted absolutely, because they 

 catch specimens from higher levels while being hauled 

 to the surface. For accurate work a closing net 

 should be used horizontally, lighter and smaller than 

 those used for true deep mid-water work, so as to be 

 workable by hand with the small reel and stranded 

 wires already mentioned ; they should carry the same 

 standard net, and be used for standard time and at 

 standard speed. 



Other points requiring study by similar methods are 

 the supposed movements of Plankton due to rain, 

 breaking seas, wind, fresh water from large rivers, 

 floating ice, and so forth. 



A curious feature well worth attention is the way in 



