1911] Kofoid: Self-dosing Plankton Net. 319 



which "worked satisfactorily" in the experimental model but 

 was not perfected for work at sea was also devised by Townsend. 

 The trips of this net are of a better type than in the net just 

 noted, but the means of maintenance of closure during descent 

 and ascent are subject to criticism since closure depends upon 

 the weight of the net upon the tow lines. Currents and irregu- 

 larities in movement due to surge of the ship or irregularities 

 in hoisting might lead to release of tension and gaping of the 

 jaws. 



A modified form of the Giesbrecht net has been devised by 

 Richard (1896), who abandoned the horizontal pressure upon 

 the wings as a means of opening the net and substituted the 

 method employed in the curtain net of the Prince of Monaco, 

 to wit, sliding the net down the cable and opening it by impact 

 on the terminal weight. He also modified the trip for closing 

 and hinged the horizontal vanes designed to keep the appar- 

 atus from Avhirling. Richard (1896) speaks well of the original 

 model, but prefers the improved one because of certainty of 

 closure. "C'est un instrument robuste, qui merite, modifie, ou 

 non, d'etre employe de preference a ceux qui ont ete decrits 

 jusqu' ici pour remplir le meme but." See also Monaco (1902) 

 and Richard (1900, 1902, 1910). 



The closing-net of Lakowitz (1896) is designed for horizontal 

 towing and is opened and closed by accessory lines which operate 

 two hinged lids on the square opening of the net. The lids 

 when closed are latched by spring catches. The closure is thus 

 exact and continuous, but the accessory lines could not be adapted 

 to work in deep water. 



The closing-net designed by Cori (1897) operates in a 

 horizontal position and is opened and closed by messenger. The 

 opening of the net is rectangular with a rim of six straight 

 pieces, long top and bottom pieces and jointed sides of two 

 pieces each. The vertical sides are jointed in their centers and 

 bend inward when the net is closed. The net is lowered closed 

 with the lower horizontal margin raised against the upper one 

 and the sides collapsed inward. The first messenger drops the 

 lower bar and thus opens the mouth of the net, while the second 

 drops the upper bar down upon the lower, folding the sides 



