324 University of Calif drnia Puhlications in Zoology. [Vol.8 



work and having a messenger which cuts loose the tow line and 

 transfers the weight to a puckering line which closes the net 

 some distance below the opening. The trip is that of the Scot- 

 tish reversing thermometer frame. The objections to the net 

 are practically the same as those to the Nansen net, with the 

 addition that the trip does not appear to be sufficiently guarded 

 against miscarriage. 



The Nansen net has been in use for a number of years by the 

 various bureaus of the International Commission for the Investi- 

 gation of the Sea, but seems not to have been described in detail 

 by any one. Figures and an account of its operation will be 

 found in the papers of Gran (1905) and Herdman (1908). It 

 is a vertical net, lowered open, drawn up for the desired interval 

 and closed by messenger which releases the crowfoot above the 

 bag transfering the weight to a strangulation cord. The net 

 is simple, easily operated, and effective. It has the defect of 

 being lowered open, and thus admits the possibility of contam- 

 ination. For mass work it is to be highly commended, but its 

 results are not critical. 



The Buchanan-Wollaston (1911) vertical net functions mouth 

 downward during descent only, and closes by a puckering string 

 tightened by a weight sliding on the standards which form the 

 frame. This net has the unique advantage, among vertical nets, 

 tluit the column of water which it filters is undisturbed by cable, 

 lines, or bars of any sort as it enters the net. The addition of 

 a double trip and some method of sending down the net closed 

 to any desired level, before opening it by messenger, would con- 

 vert this into a very valuable type of vertical self-closing net. 



A NEW TYPE OF HORIZONTAL CLOSING-NET 



The desiderata to be sought in a net for this kind of towing 

 are (1) a net closed during descent, (2) a method of opening 

 and closing entirely under control of the operator and wholly 

 free from interference by external conditions, such as irregu- 

 larities in unreeling or reeling in the cable, or by oscillations due 

 to surge of the ship, thus insuring continuity of closure both 

 prior to opening and subsequent to closing, (3) perfect closure 



