[17] FISHERIES OV THE UNITED STATES. 



filled with innumerable numbers of minute granules (Fig. 48), wliicli 

 are so small that they are barely visible wben magnified one hundred 

 diameters. They are not uniformly distributed, but are much more 

 numerous at some points than at others, and for this reason the fiuid 

 has a cloudy or curdled appearance. By selecting a place where the 

 granules are few and pretty well scattered, very careful watching will 

 show that each of them has a lively dancing motion, and examination 

 with a jjower of five hundred diameters will show that each of them is 

 tadpole shaped (Fig. 50), and consists of a small, oval, sharply de- 

 fined ' head ' and a long, delicate ' tail,' by the lashing of which the 

 dancing is i)roduced. 



"It is more difficult to decide whether the male cells are perfectly 

 ripe than it is to decide in the case of the eggs. With a magnifying 

 power of five hundred diameters, each 'head' should have a clear, well- 

 marked outline, an<#l they should be very uniform in size, and separated 

 from each other, as in Fig. 50. Under very favorable cii-cumstances 

 this i^ower should also show the 'tails' as very faint undulating lines. 



"If the 'heads' vary much in size, or if thej' are aggregated into 

 bunches, with the 'tails' radiating from the bunches in all directions, 

 or if there is much granular matter so small that the outlines of the 

 particles are not visible when magnified five hundred diameters, the 

 fluid is not perfectly ripe, and fertilization with it will not in all proba- 

 bility be very successful. 



"NUMBER OF EGGS. 



"As the male cells are infinitely more numerous than the eggs, the 

 dpe fluid from even one small male is enough to fertilize all the eggs 

 of five or six large females. 



"The number of male cells which a single male will yield is great 

 beyond all power of expression, but the number of eggs which an aver- 

 age female will furnish may be estimated with sufiicient exactness. A 

 single ripe egg measures about one five-hundredth of an inch in diam- 

 eter, or five hundred laid in a row, touching each other, would make 

 one inch ; and a square inch would contain five hundred such rows, or 

 500x500=250,000 eggs. Nearly all the eggs of a perfectly ripe female 

 may be washed out of the ovary into a beaker of sea water, and as they 

 are heavier than the sea water, they soon sink to the bottom, and the 

 eggs of a medium sized female will cover the bottom of a beaker two 

 inches in diameter with a layer of eggs one-twentieth of an inch deej). 

 The area of the bottom of a beaker two inches in diameter is a little more 

 than three square inches, and a layer of eggs one-twentieth of an inch 

 deep, covering three square inches, is equal to one three-twentieths of 

 an inch deep and two square, and as a single layer of eggs is one five- 

 hundredth of an inch thick, a layer three-twentieths of an inch thick 

 will contain seventy-five layers of eggs, with 250,000 eggs in each layer, 

 or 18,750,000 eggs. It is difficult to get the eggs, perfectly pure, and if 

 228a 2 



