i6 



Papers from the Marine Biological Laboratory at Tortugas. 



the cylinder B to fall into the position shown in figure i, B, the cylinder 

 being prevented from falling on to P2 by the check rod T, which falls 

 through Pi until caught by the knob at its extremity. The cylinder is thus 

 opened at each end by the first messenger, and the alcohol being of lower 

 specific gravity than sea-water, diffuses out almost instantaneously, causing 

 an upward flow of water through the cylinder. On sending down the second 

 messenger, which hits the lever L2, the connecting rod C2 was released, and 

 by means of strong springs the plate Pi was forced down on to the top of 

 the cylinder, which at the same time fell on to the plate P2, and thus the 

 cylinder with its sample of water was tightly closed at each end by the rubber 

 washers, the position of the parts being that shown in figure i, C. 



P.i 



p,-i 



La 



I P,-i 



Pc-i 



C2 



Li 



L2 



-W, 



B 

 Fig. I. 



R-i 



I Pp-i 



C2 \A/. 



c 



The washers with their attached pieces of thin rubber tubing had sufficient 

 capability of bulging inwards to allow for the contraction of the alcohol due 

 to the low temperature at any considerable depth, and to its compressibility 

 being greater than that of sea-water; and similarly the expansion of the 

 sample of water, as the apparatus was hauled up, was compensated for 

 by the elasticity of the thin-walled rubber tubing. It is obvious that 

 even had a slight amount of leakage occurred, a leakage inward during the 

 descent of the apparatus would not vitiate the results, as bacteria would 

 promptly be killed in the 95 per cent alcohol, and similarly on hauling up, 



