Juday—Limnological Apparatus . 
567 
net, Plate XXXIV, figs. 2 and 3, which serves for the study of 
the net plankton in deep lakes where it is not practical to use a 
pump, or in lakes where it is not convenient to carry a pump 
and hose. All of these nets consist of a truncated canvas 
cone, a straining portion made of No. 20 silk bolting cloth, 
and a detachable bucket at the bottom in which the catch 
is concentrated and then transferred to the preservative. 
Since the same bucket is used on all of the nets it may be 
well to describe it first. 
THE PLANKTON BUCKET. 
The bucket consists of a head portion (fig. 1, A, and Plate 
XXXIV, fig. 1) which is attached directly to the bolting cloth 
strainer and a detachable plankton bucket proper (fig. 1, B). 
The head and the wall of the bucket are made of telescope 
brass tubing of such sizes that the top of the bucket passes 
easily but snugly over the head piece. The surfaces which 
come into contact should be kept polished in order to insure 
ease of manipulation. The walls of the tubing are about 
0.6 mm. thick. 
The head piece, fig. 1, D, is 3.5 cm. long and has an out¬ 
side diameter of 5.2 cm. A small peg about the middle 
serves for the attachment of the bucket by means of a 
bayonet joint and two pegs near its upper edge hold the 
clamp in position. This head is attached to the bolting 
cloth by means of a clamp, fig. 1, C, which consists of two 
semi-circular pieces of bronze with wings at their ends 
through which pass the screws that hold the two pieces to¬ 
gether. The clamp is about 8 mm. wide and should be flush 
with the upper edge of the head. Each half is pierced by a 
small hole into which fits a small peg borne by the upper 
part of the cylinder. Three small loops of brass wire are 
soldered to this clamp into which lines from the framework 
at the top of the net are fastened. These lines are a little 
shorter than the bolting cloth cone and carry the weight of 
the bucket. 
The tube part of the bucket is 9 cm. long and has an in¬ 
side diameter of approximately 5.2 cm. The upper part 
which fits over the head is 2.8 cm. wide and has an L-shaped 
opening into which the peg in the middle of the head piece 
fits. (See fig. 1, B.) Below this part there are four windows 
