COLORATION OF FISHES LONGLEY. 477 



department of marine biology of the Carnegie Institution of Wash- 

 ington, her complement of men, and the diving hood and camera 

 which made the chief investigation possible and permitted a pictorial 

 record of some of the observed facts to be secured. 



As will appear from the picture, the hood affords one no protec- 

 tion from the water. It is simply an inverted, weighted, metal cylin- 

 der, cut to fit the shoulders, and connected with a compression pump 

 by a hose through which its contained air may be renewed. In prac- 

 tice its weight is slightly more than sufficient to overcome the natural 

 buoyancy of the operator. It is simple, safe, and convenient to 

 handle; yet it permits one to work upon the bottom in warm tropical 

 water for hours at a depth of 10 to 15 feet, with only one's head in 

 the bubble of air it holds. 



Provided with such a hood, and enjoying the comparative free- 

 dom of movement assured by the use of 100 feet of hose, one has 

 an unusual opportunity to observe the behavior of representative 

 marine animals under natural conditions. Most of the creatures 

 show little fear of the strange thing they see, until it is fairly upon 

 them. Schooling nocturnal fishes continue to rest idly about their 

 gathering places. Diurnal species, upon the other hand, come and 

 go, intent upon important business. Carnivorous forms, indeed, far 

 from taking flight, may even gather around one to search for pos- 

 sible food to be discovered about overturned stones, while herbivor- 

 ous types pass and repass, it may be in droves, cropping the more 

 or less dense turf of algae which covers the reefs. 



It is a strange world in which the diver finds himself; it is so 

 small and still; so surrounded by mystery; so surprisingly unlike 

 that which one imagines it to be, observing it from the surface. 

 Even when the light is brightest and the water most free from sedi- 

 ment, one never sees objects at a greater distance than a few yards; x 

 and if a heavy surf is pounding a short distance seaward, so much 

 debris may be borne inshore on the rising tide that one may be shut 

 in almost as completely as in a blinding snowstorm, and have no means 

 of finding one's way back to the boat other than following the hose. 

 No sound reaches one save that of the air rushing into the hood 

 at each stroke of the pump above. Graceful gorgonians, purple, 

 brown, yellow, or olive, may sway gently as the lazy swell rolls 

 overhead; or as one clambers about the face of some submerged 

 escarpment, one may see, from below, sheets of foam spreading where 

 trampling rollers raised by an incessant trade wind have broken. 

 Yet all transpires in perfect silence. 



A feature which contributes in high degree to the strangeness and 

 unreality of one's surroundings is the fact that while in the hori- 



1 In one instance under very favorable conditions the visibility was found to be 15 

 paces 



