280 THE GENERATIVE ORGANS OF THE OYSTER. 



we should have to class the oysters which had already acted or were 

 yet to act as females under the following categories : 



Oysters with ripe or nearly ripe ova : cultivated 21, natural 42. 

 „ „ white spat .... ,, 11, „ 19. 



Oysters with black spat .... „ 17, „ 12. 



„ which had produced young . ,, 19, „ 5. 



The table shows sufficiently well that, in this particular instance, 

 the cultivated are in advance of the natural oysters. This observa- 

 tion is confirmed by the assertion of oyster breeders, viz. that 

 natural oysters spat after those under cultivation. In the establish- 

 ments where the mass of spat to be collected is believed to be 

 derived from natural oysters, the tiles are set out some time after 

 they are set out in the cultivated beds. 



As to the age necessary for reproduction, these researches give 

 no certain information, since all the oysters received were nearly of the 

 same age. The majority were three or four years old, some few two 

 or five years. Even if the ages had varied more, the number of 

 specimens examined would have been too small to give decisive 

 results on this point. 



To arrive at a definite conclusion it would be necessary to begin 

 investigations in March, and to continue them till October. Each 

 month, at nearly the same date, at least 100 specimens both of culti- 

 vated and natural oysters should be opened. The oysters should be 

 two, three, and four years old. A section of each individual which 

 would leave no doubt as to the actual condition of the reproductive 

 organs should be made. With such materials one could arrive at 

 numbers admitting of a comparison. 



Suppose that the result still showed scarcely any difference in the 

 number of females in the two kinds of oysters, it would be rash to 

 conclude that the greater part of the free spat is not produced by 

 natural oysters. Their spat might be hardier than that of cultivated 

 oysters, and it might reasonably be admitted that the spat produced 

 by a natural oyster is larger in amount than that produced by a 

 cultivated oyster. 



