ONE-CELLED AND MANY-CELLED ANIMALS 47 



when the eggs are laid in this way they are always produced 

 in great numbers. An average sized oyster will produce 

 during the season about 16,000,000 eggs and a large old female 

 may produce more than three times that many during the few 

 summer months that she is breeding. The number of sper- 

 matozoa that are produced by a male oyster is simply incon- 

 ceivable, and the water in the vicinity of the oyster beds is 

 literally swarming with these minute cells during the breeding 

 season. These enormous numbers are made necessary by 

 the fortuitous mode of fertilization. It is a condition compar- 

 able with that of the great production of pollen and chance 

 method of pollination in the case of the pines and other wind- 

 pollinated flowers. 



Other aquatic animals, as certain fishes, lay their eggs in a 

 more or less carefully prepared nest, and the male soon passes 

 by and deposits the milt, which contains the spermatozoa, 

 over them. With most of the higher animals, however, the 

 ova are fertilized while still inside the body of the mother, and 

 various provisions are made for transferring the spermatozoa 

 from the male to the female. 



