A PINK YEAST CAUSING SPOILAGE IN OYSTERS. 23 



moisture which collects at the bottom of the pile during months 

 in which tliey lie in the yard. When these shells are taken to the 

 beds it is probable that large numbers of the pink yeasts are carried 

 with them. 



As a method of control it is recommended that all the bins, 

 benches, tubs, etc., be scrubbed thoroughly with water and then 

 washed with a 0.04 per cent solution of formaldehyde gas, which is 

 equivalent to 1 part of formaldehyde to 2,500 parts of water. Such 

 a solution may be prepared by adding 1 part of commercial formalin 

 to 1,000 parts of water. The washing should be done in the fall, 

 before any oysters are brought to the opening house; and bins, 

 benches, tubs, etc., should also be washed several times during the 

 winter whenever convenient. 



SUMMARY. 



1. The organism causing a pink color in shipped oysters is a yeast- 

 like fungus. 



2. This pink yeast was found in large numbers in the oyster house 

 and on the utensils in and about the house. Of the examinations of 

 the house and utensils 73.9 per cent were positive. 



3. The yeast was found less frequently in oysters before they were 

 brought to the oyster house. Of the oyster samples analyzed 20'.3 

 per cent were positive. 



4. Occasionally the yeast was found in deep and surface water 

 samples from the oyster beds. Three and six-tenths per cent of the 

 deep samples and 2.8 per cent of the surface samples were positive. 



5. The yeast was not found in mud samples from the bottom of the 

 bay. 



6. The yeast is elliptical, measuring 6 by * micra. It reproduces 

 by budding and does not form spores. Staining by Gram's method 

 is peculiar. 



7. The yeast grows at room temperature (21° to 25° C), and 

 does not grow at 37° C. The best medium for its growth is dextrose 

 agar, although it can be grown on gelatin, potato and blood serum, 

 and in broth and milk. 



8. The yeast does not produce acid, gas, nor alcohol in carbohy- 

 drate media. It inverts saccharose. It does not produce indole nor 

 phenol. It reduces nitrates to nitrites and ammonia. 



9. The yeast produces a pink pigment which is insoluble in water, 

 slightly soluble in alcohol and carbon disulphid, somewhat more 

 soluble in chloroform, and very soluble in ether. 



10. The yeast grows abundantly in the absence of oxygen. Its 

 thermal death point is 64° C. The limits of alkalinity and acidity 

 for its growth are —0.8 and -[-10.5. It grows best between -(-0.3 and 

 +2.0. It resists drying for at least 100 days. 



