300 



SCIEXCE. 



[Vol. VII. , No. 165 



to open the route to commerce. The boundary is 

 to be determined, and then operations will com- 

 mence at once. 



The services of M. Thouar have been recognized 

 by the Bolivian congress, winch has voted him a 

 gold medal, five square leagues of land, and thirty 

 thousand francs, for the publication of his maps 

 and reports. The Argentine government has 

 promoted the officers of his escort, and given a 

 month's extra pay to the private soldiers. The 

 explorer himself will devote himself to the per- 

 fection of the methods projected for the promo- 

 tion of commerce on the Pilcomayo. 



SURFACE-COLLECTING ON THE ALBA- 

 TROSS. 



During the past year surface-collecting has 

 been very successfully carried on by the fish- 

 commission steamer Albatross, and not only have 

 many additions been made to the surface-fauna 

 off our coast, but, what is at least of equal im- 

 portance, rare forms have been taken in numbers 

 sufficient for detailed microscopic study. 



The nets chiefly employed in this work are ten 

 feet long and of ha If -inch mesh ; then- mouths are 

 four feet in diameter. The outer two-thirds are 

 lined with a fine webbing, and the end is closed 

 by several turns of stout lashing put on with care, 

 to protect these linings from strain. They are 

 suspended from the swinging Looms, and. five- 

 eighths submerged, towed at the rate of two knots 

 an hour ; each net, under these conditions, strain- 

 ing nearly twelve thousand gallons of water per 

 minute. They are not, of course, adapted to the 

 capture of the smallest forms of life, for which 

 purpose fine silk nets of much less diameter are 

 employed. 



As might be supposed, the amount of material 

 taken in this way is large. When surface-life is 

 at all abundant, surface-fish and the young of 

 some bottom-fish, the mature and immature forms 

 of Crustacea, various pelagic forms of mollusca, 

 and jelly-fish of all sizes, are represented in the 

 average haul. 



Perhaps special mention should be made of the 

 capture of argonauts and of several species of file- 

 fish (Balistidae). Argonauta argo has been taken 

 a number of times clinging to gulf-weed ; and a 

 fine specimen of another species of argonaut was 

 taken from the under surface of a jelly-fish, to 

 w hich it tenaciously clung. Unsuccessful efforts 

 Ikivc been made to bring in alive argonauts cap- 

 tured during the short summer cruises of the 

 steamer from Wood's Holl, Mass.: perhaps failure 

 was due to the change from the warm water of 



the Gulf-Stream region to the cold water inshore. 

 In an aquarium these animals swim about with a 

 slow, undulating, rhythmic motion, sometimes 

 holding themselves poised for a while, and then, 

 by a sudden turn of the siphon, darting with ease 

 in any desired direction. When swimming, the 

 expanded and partially transparent membrane of 

 the dorsal arm adheres so smoothly to the side of 

 the shell, that it requires close observation in a 

 strong light to detect the fact that it is covered. 



The file-fish is found under gulf-weed, and is 

 captured when the ship slows down for dredging 

 or sounding. A specimen of this fish three inches 

 and a half long, together with a piece of drift- 

 wood covered with barnacles (Lepas), was placed 

 in an aquarium. It immediately began to prey 

 upon the barnacles thus : holding itself in readi- 

 ness, it waited for the intended victim fully to 

 extend its cirri, which the fish then, by a sudden 

 onslaught, seized, and, backing swiftly away, 

 dragged the greater portion of the animal from its 

 shell. The attack of the fish was not always well- 

 timed, and, failing in its purpose, its solid jaws 

 brought up with a sharp click against the closed 

 shell within which the coveted morsel had safely 

 retreated. 



Science has already noted the fact that the 

 electric light is an important aid in surface-collect- 

 ing. A single Edison-light bulb protected by a 

 wire cage, and furnished on the upper side with a 

 shade, is lowered a few inches under water by an 

 insulated cable, which is then made fast. Light, 

 silk bolting-cloth scoop-nets, fastened to long- 

 bamboo poles, are held in readiness above the 

 illuminated area. The larger part of the material 

 collected by these nets, especially in shallow 

 water, is composed of small Crustacea and worms, 

 which the light often attracts in Swarms. 



At Wood's Holl, small schools of herring 

 (Clupea) frequented the lighted area to devour the 

 sexual form of certain worms (Nereis limbata and 

 N. megalops). A number of specimens of this 

 fish were taken with flies improvised to resemble 

 these worms. The argonaut has been captured 

 under the light, probably by accident. Squids, 

 however, appear in numbers, apparently allured 

 from some distance. The flying-fish often swims 

 sluggishly towards the light, its wing-like pectoral 

 fins more or less extended on the surface of the 

 water, and quite motionless. If startled, it rises 

 instantly in the air, and disappears in the dark- 

 ness like a frightened bird. When taken un- 

 harmed from the scoop-net, it exhibits a win-- 

 movement like that of the humming-bird or 

 sphinx-moth, and seems to demonstrate its claim 

 to true flight. 



With the abundant material for close structural 



