Plankton Catcher — Bary ET AL. 
49 
Fig. 4. The parts of the catcher displayed and showing their approximate relationships. For legend, see Table 1. 
Radial fins (2, 4, c") attach to its inner sur- 
face and to a central, stainless steel, spindle 
(2, 4, d) which protrudes forward from the 
valve and guides the valve, and around which 
a groove (2, d ") has been turned. When 
closed, the leading edge of the valve abuts 
against the trailing edge of a streamlined boss 
(2, 4, a), set in the mouth, and the forward 
end of the spindle closes a hole of 1 5/16 
in. diameter (2, a'") in the front of the boss. 
A faring (2, 4, a') extends rearward from the 
boss to improve streamlining. Four holes, 
3/16 in. diameter, pierce the front end of the 
boss. When the unit is raised from the water, 
air enters by these and enables entrapped 
water to escape freely. 
The valve is opened by pushing the spindle 
towards the rear with a thruster or loader (4, 
u) through the hole in the boss. This com- 
presses a coiled spring (2, 4, d' ), fitting 
round the spindle. The valve is locked open 
by a spring-loaded, radially mounted, detent 
pin (2, 4, c'") which clicks home in the groove 
turned in the spindle. The pin is withdrawn 
from the detent position when the release arm 
(1, 2, 4, g) is actuated by the weight of a 
messenger (4, v\ 6, 7). The spring-loaded 
spindle is thus released and moves the at- 
tached valve rapidly forward, shutting off the 
flow of water to the net. 
The filtering net (Figs. 2, 3, 4, h) is of 
stainless steel mesh; joints are folded, spot 
welded and then sealed with "Araldite.” The 
ratio of the total area of the filtering holes 
and the valve (see below) of the catcher is 
approximately 11 for a net of 40 meshes to 
the inch and 14 for a net of 10 meshes to the 
inch. A frame encloses the net. It consists of 
three tubular brass struts (1, 2, 3, 4, k) at- 
tached to a forward clamp ring (2, 4, k'), 
