112 
At the spawning season the eggs and milt are shed, 
and drift about in the sea. Fertilisation then takes place 
as deseribed above. 
The eggs of all the flat fishes, and of most round 
fishes (the cod, haddock, whiting, gurnard, sprat, &c.) 
float near the surface of the sea. The eggs of the skate, 
rays and dogfishes, herring, and some other fishes (which 
are not used as food) sink to the bottom, and pass through 
their development there. 
The average number of eggs spawned by a single 
female fish in the course of one season are :— 
In the Turbot ... eh a 8,600,000 
5 od oe BS. ee 4,500,000 
os ie Oleg a2 2 oe 570,000 
» Haddock ae rae 450,000 
js,” pe eGes he ey. ae 300,000 
, Whiting ey ee: 120,000 
<a) blerrimnat. oe ie 31,000 
» Skates, rays and dogfishes, about a 
dozen or less in the season. 
THirp Day. 
The Mussel. 
The structure of the mussel.—tThe 
mouth and stomach; the gills; the mantle; the foot or 
ce 
“tongue ’’; the byssus or “ weed.” 
The feeding of the mussel.—tThe mussel 
feeds “by suction.” Its food consists of exceedingly 
small animals and plants that float about in the water. 
The water containing this food is sucked into the cavity 
of the shell and the food is then taken into the mouth. 
The mussel breathes by means of its gills. When the 
vill is examined under the microscope it is seen to consist 
