47 



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 42 L 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 pro- 

 duce 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. Eegarding 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 iu 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 Pocomoke 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 safe to take about 50 per cent, from the beds, supposing them to 

 be in good condition. That is but an estimate, and may be an erroneous one, but certainly it is 

 not too small. It now remains to be seen what number of oysters are actually removed from the 

 beds. I regret that statistics of the oyster trade in the Sounds are not at hand for reference, and 

 also that the pressure of other work while I was in that locality prevented me from obtaining 

 them. Such observations as we were able to make, however, will furnish a basis for a somewhat 

 rude estimate of the number of oysters and young taken oft' the beds during the season. 



While in Crisfield Harbor, about the 11th October, we counted fifty-seven sail oyster dredgers. 

 The number of bushels carried by them was estimated, and the estimate subsequently verified by 

 the statements of the masters of the several vessels in each class. The following table shows the 

 result for one day: 



Table I. 



Class. Number. 



1 

 Average nura- 

 Nurnber of ber of bush- 

 bushels, els to each 

 sail. 



Class of vessel. 



Number. 



Number of 

 bnshi Is. 



Average num- 

 ber of bush- 

 els to each 

 sail. 



Schooners | 37 



Sloops 12 



2,075 • 56 

 256 1 21 



Buckeyes 



4 



4 



45 

 32 



11 



8 



Total '. 





Total 



2, 331 



77 







77 









Grand total 



2,408 



1 





The day had been a bad one for dredging, and but a small number of dredgers had been at 

 work, and they had come into port much earlier than usual ; consequently the average and total 

 number of oysters are below the usual figures. On the same day, in order to ascertain the number 

 of young attached to the mature oysters that were taken off the beds, I had three samples, of .a 

 peck each, selected from different vessels entering the harbor and the number of young on the 



