114 THE OYSTER. 



towns. They are eaten in Paris especially as the 

 greatest delicacies. The general opinion of the 

 oyster proprietors residing on the Eoach is, that the 

 green ribbon weed, which grows so abundantly in 

 that stream, is the cause of their peculiar appear- 

 ance. This weed begins to grow in the latter part 

 of the summer and lasts till March. It dies in 

 March, and ; a fresh lot begins to grow. The oysters 

 are therefore, it will be seen, green when the weed 

 is in full development, and not while it is growing. 

 It has been suggested that the cause of the green- 

 ness is the presence of sulphuret of iron derived 

 from the " cement stones," which contain nodules 

 of iron pyrites. 



The oysters at Marennes in France are also 

 highly esteemed by the French people for their 

 greenness. The green oysters from the Eoach have 

 been analysed by Dr. Letheby, who reports that 

 the green tint is due to a natural pigment which 

 does not contain a trace of copper or other dele- 

 terious matter ; the oysters therefore are perfectly 

 nutritious and wholesome. 



We will now pass on to the development of the 

 spat or young oyster, and the causes favourable or 

 unfavourable for its development. The greater 

 portion of oysters spat about the end of June or 

 beginning of July, the oyster at the immediate 

 time of depositing its spawn being filled with a 



