METHODS OF COLLECTING AND PHOTOGRAPHING 



75 



Fig. i8. Bucket of Wisconsin plankton net. From 

 apparatus loaned by Professor Birge. At right is one 



oft " ■ 



scriptions see text. 



[ the writer's tubes for filtering plankti 



(From original photographs.) 



For de- 



the inside of the band, with its margin turned back over its outei 



surface for the fraction of an inch. By this construction the canvas 



cone folds conveniently for transportation, while the inner surfaces 



of cone and net are continuous and smooth, so that plankton 



organisms do not readily lodge 



on them. If convenience in 



transportation is not important 



the cone may be better made 



of sheet brass. 

 The original feature of this 



net is the bucket (Figs. i8 and 



19), which is made of telescope 



tubing of two sizes. The smaller size (two inches in internal 



diameter) is used to make the headpiece shown attached to the net 



in Fig. 17. This (Fig. 19, a) is one 

 \ and three eighths inches long and is 

 fastened to the net by means of a 

 brass band clamp (Fig. 19, h) made of 

 two pieces, with wings at the ends 

 through which pass clamp screws. 

 A pin soldered into the headpiece 

 fits a hole in each half of the clamp 

 and prevents its turning when the 

 bucket is twisted to remove it (seen 

 near the upper margin of Fig. 19, a). 

 Three brass rings soldered to the out- 

 side of the band clamp serve to attach 

 cords which extend to the lower sup- 

 porting ring of the canvas cone and 

 carry the weight of the bucket. 



The bucket (Fig. 18) is made of tele- 

 scope tubing of a size which fits over 



., j, millimeter scale. For description see , 



text. (Frorn original photograph of appa- that used for the hcadpiece. Plcces 



ratus loaned by Professor Birge.) *■ 



are cut from the sides of this so as 

 to form four windows separated by strips about one-half inch wide. 

 These strips are strengthened by soldering to the inside of each a 

 semi-cylindrical rod about one-quarter inch in diameter (Fig. 19, A). 



Fig. 19. Headpiece and bucket of the Wis- 

 consin plankton net. a, headpiece; b, 

 headpiece clamp; c, bucket; d, e, lower and 

 upper band clamps; /, one of the side 

 clamps with screws; g, side clamp in posi- 

 tion; h, semi-cylindrical rod soldered to 

 strip between windows; i, stem of the plug 

 which closes the spout seen below at left of 

 *, millimeter scale. For description see 



