104 OYSTERS, AND ALL ABOUT THEM. 



black-sick and white-sick, I have never been able to dis- 

 tinguish any difference in the form of the spawn, the fact 

 being that the spawn is always white until it quits the 

 ovary, and then becomes black. The cause of the exuda- 

 tion of the white is easily accounted for by the ovary being 

 heavily loaded, and the oyster, when disturbed, closing its 

 shell. I have seen both white and black spawn escape 

 into the same basket, from the same causes. 



" The Burnham dredging also tends strongly to cor- 

 roborate this opinion, being quite the end of the spawning 

 season, and there being no white spawn observed, although 

 some were black-sick. I have endeavoured to compute the 

 number of young oysters between the branchiae of a single 

 old one in the following manner : Having collected them 

 all with a camel-hair brush, and placed them in strong 

 spirits for twenty-four hours, I dried them on blotting- 

 paper the spirits having removed the glutinous matter, 

 then weighed a tenth part of a grain, and counted the 

 number of young in it (2500). The total weight of the 

 whole was 72 grains, which, multiplied by 10, and again by 

 2500, gives 1,800,000 as the total number of young oysters 

 in one old one. I do not mean to say that this calculation 

 is precisely correct, there probably having been some loss ; 

 but, at all events, it is a pretty near approximation." 

 " History of the Oyster." 



Early in August, 1865, Frank Buckland wrote to the 

 Times: "Just now the oysters at the mouth of the 

 Thames are in full ' black spat ' -that is, they are just 

 ready to send forth the young oysters (technically called 

 'spat') (e] from their shells. The way to ascertain this, 



(e) " It is'unfortunate that the same word ' spat ' should be applied 

 to things so different in their nature, as the eggs and unhatched young 

 of the oyster, contained within the mantle cavity, on the one hand, and 



