478 ANNUAL REPORT SMITHSONIAN" INSTITUTION, 1918. 



zontal plane one's world suffers diminution, all vertical distances 

 prove to be much greater than they appear from the surface of the 

 water. Apparent smooth bottoms are rough ; rough ones are seamed 

 by crevasses ragged with overhanging ledges, or are pitted with holes 

 scoured by the waves and communicating with one another at times 

 beneath natural bridges. Yet, however rough the bottom, one carries 

 one's load of metal with ease, since its effective weight is so greatly 

 reduced in water. One even scales near- vertical precipices without 

 difficulty, for the same reason. But, light as one feels, real speed is 

 out of the question, and the horizon is very near. It is therefore 

 well, perhaps, that upon every hand interesting things claim one's 

 attention, or active imagination might dwell too much for comfort 

 upon terra incognita which the hood's one narrow window permits 

 even to touch one from the rear. 



The animal life on a rich tropical reef w T ill engross the powers of 

 observation of a naturalist for an indefinite period, even if he is 

 able to study it only from a boat through a water glass ; but its appeal 

 to his interest is intensified when he is able actually to stand upon 

 bottom, beneath water, in the very midst of the creatures observed. 

 This is due to several factors. Limited as one's range of vision is 

 by the opacity of the water and its suspended sediment, one still 

 sees more and more clearly upon the whole, when submerged than 

 under any other condition. No reflection from the water's surface, 

 and no inability to manipulate one's water glass satisfactorily, robs one 

 of the last act of innumerable dramas staged by the reef population. 

 Again, many of the most interesting creatures to be seen, or features 

 in their behavior, can not be made out clearly at distances which must 

 intervene between them and an observer at the surface. Finally, 

 fishes in particular, among marine animals, are not adjusted alone 

 to a world beneath them. One needs, therefore, in many instances 

 to see them from below, against what lies above, in order to grasp 

 the full meaning of their coloration. 



Some of the glimpses a diver catches of the normal lives of the 

 animals by which he is surrounded are highly instructive. He may 

 find, for example, even on what seems the loose and shifting sand 

 of a submarine Sahara representative species whose habits and 

 structure accord with their surroundings. There are flounders there 

 marked with the color and pattern of the bottom beneath them, which 

 while he watches will bed themselves and be lost from sight in an 

 instant, except as their prominent eyes rise beyond the general surface 

 of the body, and above the drifting sand, keep watchful outlook upon 

 local happenings. Pale, hatchet-faced razor fishes of one genus or 

 another may also be in evidence, sidling away leisurely as he advances, 

 and ready ever to demonstrate the ease with which their peculiar form 

 enables them to cleave the sand, dart from sight, and lose them- 



