302 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



tbe disease is not among the number of the parasites of man, and also 

 because it is inevitably killed by cooking the crawfish. 



In conclusion, I would add that according to Mr. Oscar Micha, who 

 carries on both at Berlin and at Cologne a considerable trade in craw- 

 fish, a few very young crawfish are beginning to reappear in many of 

 the streams where extermination was complete and where no attempt 

 at restocking has yet been made. Koav, as in these streams no adult 

 crawfish was able to escape destruction — when, on the one hand, the 

 immigration of individuals coming from uucoutamiDated localities seems 

 improbable, and when, besides, we meet no specimen of an age capable 

 of reproduction — we are led to think that the young crawfish which ap- 

 pear were born before the invasion of the epidemic, which they alone 

 have been able to resist. In this case the imniunity which they would 

 have enjoyed should be attributed to the fact that the very young crawfish 

 have the habit of burrowing and passing the first part of their existence 

 at a great depth in the beds of the rivers. In their holes, where they 

 often are more than a meter [yard] from the water, no doubt they can 

 escape the action of certain noxious influences and of certain principles 

 of disease carried by the water. Thus it could be explained how the 

 epidemic, which could have brought about the disappearance of all the 

 crawfish of a river, has nevertheless spared those crustaceans which 

 were out of its reach under the protection of a thick layer of earth. New 

 observations will doubtless i^ermit it soon to be settled in this respect. 



160.-FliOAT8 FOR THE SO-CAL,I.ED FATTEIVIIVO OF OV8TFRS. 



By JOIIf* A. fSYDER. 



[From a letter to Prof. S. F. Biiird. ] 



You have sent me some letters regarding Weems's floats for fattening 

 oysters. What their structures are like 1 do uot know, but doubtless 

 some one has a patent on them. 



The simplest and most practical structures of the kind which I have 

 seen are. the storage and fattening floats used by Mr. Conger, of Frank- 

 lin City, Md., and now in use by all the shippers and planters in the 

 vicinity of Chincoteague Bay. I have already described them briefly 

 in my i)aper on the result of the work at Stockton, although I have 

 been informed that similar structures, or rather structures serving sim- 

 ilar i)arposes, are in use on the oyster-beds along the shore of Stateu 

 Island, ISTew York. 



It is probably a fact that in all of these contrivances they take ad- 

 vantage of the effect produced by fresher water upon oysters which 

 have been taken from slightly Salter water. The planters of Chinco- 

 teague call this " plumping the oysters for market." It does not mean 



