Juday—Limnological Apparatus. 573 
alcohol. These vials are more convenient than the larger 
bottles for storing a large number of catches. 
THE LARGE NET. 
In 1911 a study of the chemical composition of the net 
plankton was begun and, in order to obtain a sufficient 
amount of material for these analyses, it has been necessary 
to strain several thousand liters of water. This required a 
net with a fairly large straining surface and the large net 
was designed to meet this need. The opening of the trun¬ 
cated canvas cone is 25 cm. in diameter and the lower ring 
is 30 cm. in diameter, while the length of the cone is 33 cm. 
The length of the bolting cloth cone is 70 cm. (Plate XXXVI, 
fig. 1.) With the exception of size this net differs from the 
small one in only two minor points. The framework of the 
canvas cone consists simply of two brass rings and the whole 
net is suspended from three hooks attached to the upper 
ring. When in use the net is suspended inside the large can 
shown in Plate XXXVI, fig. 2 and the hooks are so adjusted in 
length as to fit over the top of the can. 
THE CLOSING NET. 
The closing net consists of a truncated cone made of 
heavy muslin or light canvas, a straining cone of bolting 
cloth, a removable bucket, and a simple release. (See Plate 
XXXIV, figs. 2 and 3.) The framework of the top cone con¬ 
sists of two rings of brass wire. The ring at the mouth of 
the net is 12 cm. in diameter, while the lower ring is 17 cm. in 
diameter. The upper cone is 40 cm. long. The bolting cloth 
cone has a length of 47 cm. 
The release is made of brass and is shown in fig. 3 and Plate 
XXXVIII, fig. 3. It consists of an outer, hollow cylinder, a 
plunger, and a spring. The cylinder is 2.2 cm. in diameter and 
5.8 cm. long. The opening within it is 1.6 cm. in diameter 
and extends down to within 4 mm. of the lower end. This 
last part is pierced only by a hole large enough to accommo¬ 
date the line on which the release is used, which is 6 mm. in 
the one described. On one side of the cylinder a slot 3 mm. 
wide extends down from the top for a distance of about 3.7 
cm. This slot is occupied by the curved, holding arm on the 
