RESUME OF THE STAGES OF DEVELOPMENT 87 



opportunity to subject it to a practical test, but it may be worth following 

 up with a view to becoming able to judge of the age of oysters. 



If the above suppositions are correct, then male oysters become sexu- 

 ally mature at a time when they exhibit only one complete year's growth 

 (1 inch), but when they are beginning their second year's growth, and are 

 really in the third summer of their existence. During the first autumn 

 they grow to \ inch or thereabouts and then rest; with the arrival of warm 

 weather the next summer they begin and carry on a vigorous growth until 

 again arrested by cold weather and scarcity of food; in the spring and early 

 summer of the following season they set about developing the reproduc- 

 tive organs and begin a new period of growth. 



In a retrospect of the processes of spawning, swarming, and spatting, 

 the time of the year mentioned for each is of course the beginning of the 

 process. If it were possible to observe, and to confine our attention to a 

 single egg, naturally spawned, and, under normal conditions, watch its 

 development, the matter would be simplified in that the processes would 

 be separated and follow in the order named. If it were possible to ob- 

 serve a single oyster, taking its natural course, and to watch the develop- 

 ment of its spawn, under normal conditions, there would be somewhat 

 greater complexity; even if the eggs were all extruded* at once some of 

 them would soon begin to develop faster than others, with the result that 

 the succeeding processes would to some extent overlap. On an oyster 

 bank there may be millions of oysters; they spawn millions of millions of 

 eggs — each oyster when its eggs are ripened or it feels the impulse; the 

 first oysters spawn considerably in advance of the last ones. In an oyster 

 area of different beds under widely divergent physical conditions, the first 

 oysters spawn the whole length of the spawning period before the last ones; 

 spawning, swarming, and spatting may overlap, to the extent that the 

 first brood may reach the spat stage before the last eggs are spawned. 

 Matters become so complicated that the observer may have any or all 

 stages between and including the extremes presented to him at once. He 

 then loses sight of individuals and thinks of aggregates and processes. 



Viewed as a whole, each of the processes of spawning, swarming, and 

 spatting begins with a minimum number, rises to a maximum, which is 

 held for a time, and then commences to decline. Spawning is first com- 



*With regard to the extrusion I may mention a single case. I was busy in the 

 cabin doorway of the "Ostrea," opening oysters to procure ripe eggs and sperms. At 

 times the sun shone upon a little heap of oysters on the deck in front of me. I suddenly 

 heard a squirting noise and looked to find one of the upper oysters nearly covered with 

 a discharge of eggs. The occurrence does not prove however, that this is the normal 

 method of extrusion, since the oyster may have been irritated by the heat or by a jar, 

 and suddenly snapped its valves towards each other, pressing on its body and forcibly 

 squeezing what eggs were already ripe from the oviduct. The normal discharge may 

 be more of the nature of a gradual flow of those eggs that become ripe and free, backed 

 up by the pressure of growth behind or by the ordinary movements of the body. 



That eggs of the same brood do not develop uniformly can be seen in a beaker 

 containing the products of any fertilization experiment. 



