312 TJniversiti) of California Puhlications i)t Zoology. [Vol.8 



the cable and lowered closed; released by messenger at the 

 desired level, it slides down the cable to a buffer which stops 

 and again closes it. It is held closed by its own weight. This 

 apparatus can be used only in a vertical direction, is small, and 

 any increase in size involves difficulties in its clamping to, and 

 release from the cable. As constructed there is a possibility, 

 readily obviated by a spring catch, of the surge of the vessel, or 

 irregularities in heaving in the cable, temporarily opening the 

 bottom of the trap. This apparatus was used by Agassiz (1888a) 

 on the "Blake," but has not been generally adopted or devel- 

 oped. The recently devised vertical net of Buehanan-Wollaston 

 (1911) is the nearest approach to it in working principle. 



The protozoan trap of Cattaneo (1882), devised for collecting 

 the bottom fauna of Lake Como, functions only upon striking 

 a substratum. It is really a water-trap some of whose principles 

 are developed in later patterns of water-buckets (see Kofoid, 

 1906). 



The first plankton net for horizontal towing seems to have 

 been devised by Pavesi (1883) for use in Italian lakes. It is 

 lowered while open, and its lateral semicircular jaws are closed 

 by a spring released by a messenger. This net is of frail con- 

 struction, not adapted for deep-sea work. There is nothing to 

 prevent its functioning as a filter, partially at least, during 

 descent, and the closure is neither exact nor certain. 



The closing-net devised in 1882 by Captain Palumbo of the 

 "Vettor Pisani" Expedition described by Chierchia (1884, 1885, 

 see also Richard, 1908) was so constructed that the pressure 

 against the water during descent was expected to keep the net 

 closed and that it would open upon ceasing to descend. The 

 propeller mechanism of a Miller-Casella reversing thermometer 

 was employed to close the net. This was placed above the net 

 and released a weight whose pressure was expected to hold the 

 net closed. Chierchia (1885) regards the closure as inadequate, 

 and Chun's trials of a net of the Palumbo pattern led him to 

 reject it as unsatisfactory. Agassiz (1892) has criticized it 

 on the ground of incomplete closure and possibility of reopening 

 during descent. The net of Imhof (1885) was never adequately 

 described, while that of Turbyne (1885) was adapted to vertical 



