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bulletin oe the bureau of fisheries. 
show inability to close except in the advanced stages of oxygen starvation. That oxygen 
consumption by tar may help to account for the fact that oysters are injured by stag- 
nant tarry water, while they are iminjured by the tar in running sea water, is quite 
probable. In the natural habitat of the oyster, however, it seems quite impossible 
that the slight reduction of dissolved oxygen which small amoimts of tar could effect 
would alter the results of oyster culture. 
CONCLUSION. 
These experiments show no noticeable effects of water-gas tar on oysters in con- 
stantly renewed sea water. This is true in spite of the fact that large amounts of tar 
mixed with stagnant sea water, or small amounts injected into oysters which are kept 
in stagnant water, do cause serious or fatal effects. Considerable quantities (1.5 c. c.) 
may be put inside the shell of an oyster kept under conditions resembling those of its 
natural habitat without causing any effect. The harmlessness of the tar under these 
circumstances is due apparently to the ability of the oyster to rid itself of such foreign 
matter. In stagnant water the organism can not be effectively washed out, and effects 
involving a loss of sensitiveness in the mantle result. That consumption of the dis- 
solved oxygen in the stagnant water by tar may have some effect on oysters is a 
possibility. 
