36
VICTOR L. LOOSANOFF AND HARRY C. DAVIS
blood cells and body fluids accompanying the spawning, we use a series
of stainless steel sieves with screens containing different numbers of
meshes per linear inch (Fig. 17). The finest screen that was found
practical in our operation has mesh openings averaging 44 p, but since
many mcahes arc actually larger and exceed the diameter of an oyster
cgg, which is i ~ l i o i i t !iO p , 1riiiii.y qpi pn~n throuKh tho Hievc!. I t i H
true t h a t I)y using No. 26 bolting silk n smaller Hize meHh is available
but in that case the openings are so small that they eaxily get clogged,
rt~ridi:riiig tliv a i ( ~ w s
u ~ i : l w n . As th rwi~lt, in our practice we UHC a Hcrics
of N i w i L s , tjlw f i w n t of which h w H iiominal opening of about 44 p,
followed, WJNW ~ic~cc~ssnry, t)y an!, of thv coarser screens with openings
0 f 5 3 , ti2, 74, t(H, 120, 126, 14!) nlid 177 p.
In spccies having eggs too small to be retained even by our finest
screen, the eggs can be partially freed of body fluids, sperm, etc., by
letting the eggs settle on the bottom of a dish and then syphoning or
decanting most of the fluid. By repeating this procedure several
times most of the undesirable substances t,hat are dissolved or suspended
in the water will he discarded.