826 OYSTERS, AND ALL ABOUT THEM. 



Professor Mobius to be those descendants of the market- 

 able ones that have survived their most precarious years of 

 existence, and escaped their principal enemies, and are 

 consequently likely to reach their full growth. They thus 

 represent the total number of embryos spawned which have 

 survived in the struggle for existence. 



From his (Mobius') experiments he decides that an 

 oyster spawns about 1,000,000 embryos in a season, and 

 that 44 per cent, of the mature oysters give forth " spat." 

 [Other authorities are of the opinion that only about 10 

 per cent, spawn ; Professor Mobius' data appear hardly 

 sufficient to justify his conclusion.] 



From the above it is evident that in an assemblage of 

 a thousand oysters, 440,000,000 embryos will be voided 

 every season, and of them 421 would survive, or 1,045,000 

 embryos would be destroyed where one was preserved. 

 But the medium-sized oysters also spawn, though they 

 send forth a much smaller number of embryos. Mobius 

 estimates that the 421 in the community would produce 

 about 60,000,000 of " spat." It would therefore require 

 about 500,000,000 embryos to produce 421 medium oysters, 

 or 1,185,000 to produce one. Regarding these results, 

 Professor Mobius is of the opinion that no more than 40 

 per cent, should be removed each year ; but, in my opinion, 

 in order to maintain the oysters at a constant number in 

 the above case, no more than 25 per cent, should be 

 taken, as the one oyster in four would be replaced each 

 year. No comparison between the Schleswig-Holstein 

 beds and those on our coast can well be instituted, but as 

 the beds in Tangier and Pockomoke Sounds are of greater 

 extent, and as the more extensive the bed the greater the 

 breeding power, I should consider that, until the annual 

 number of mature oysters produced is known, it would be 



