76 FRESH-WATER BIOLOGY 



The bottom of the bucket which is conical and ends in a tapering 

 spout is shrunk into place flush with the lower edge of the windows, 

 after heating the bucket in a jet of steam. A taper plug of brass, 

 with a long stem (Fig. 19, i) which ends in a milled head, is 

 inserted from within and closes the spout. The edge of the 

 bucket has an L-shaped incision which receives a pin soldered 

 to the outside of the headpiece so as to form a bayonet catch 

 which holds the bucket in place on the headpiece. The four 

 windows in the bucket are closed by a single piece of bolting 

 cloth, held in place by a band clamp at top and bottom (Fig. 19 

 d, e) and by four side clamps g screwed between the windows. 

 The holes for the screws are conveniently burned through the 

 bolting cloth with a hot wire. 



A cheaper bucket described by Kofoid (1898) is shown in section 

 in Fig. 20. It is a cylinder of sheet copper around the top of which 

 are soldered two light-wire rings, which serve to 

 hold in place the string s, which ties the tip of the 

 net to the bucket. In the sides of the cylinder are 

 cut three equidistant windows, each one and one- 

 half by one and three-quarters inches, which are 

 closed by brass wire gauze wg, soldered to the 

 edges. Gauze containing two hundred meshes 



Fig. 20. Simple townet ,. . , n r i 



bucket as seen in sec- per linear inch answers very well for these wm- 



tion. b, conical bottom. r i i • 



(i/>, drip point rr', wire dows. The bottom of the bucket IS a cone of 



rings soldered to top of 



whkh'ti of net'lftied ^opper with a central opening which continues 



'the't^wi^e'ringr™ into a short, obliquely-pointed tube t. The open- 



fo^'emp'yfnf bucke?^ ing is closcd by a rubber stopper with a wire 



of^'tte'^thrertindows handle which extends above the top of the bucket 



cut in sides of bucket. i • i . • i • 



The rubber stopper with and IS bent mto a loop. 



wire handle is seen at 



center of bucket. (After The net IS constructed like the townet, except 



Kofoid.) _ _ ' f 



that the tip is cut off at the point ij (Fig. 16) 

 and the silk sHt along the dotted lines between gh and ij to 

 allow for the fitting and fastening of the bucket in place. 



The plankton net is drawn from the bottom to the surface, 

 and the organisms that have been caught in it are washed into 

 the bucket by throwing water onto the outside of the net, or by 

 sousing it in the water. The net is then lifted above the water, 



