PROGRESS IN BIOLOGICAL INQUIRIES, 1936 41 
eration to a definite spawning area. The observations made here, 
owever, point to the theory of specific chemical attraction. 
With an average temperature of 28° C. and salinity ranging from 
25 to 35 parts per thousand, the eggs begin to hatch 20 days after 
the capsules are deposited. The length of the free-swimming period 
is unknown since efforts to keep the newly-hatched larvae in special 
jars have been unsuccessful. 
Several experiments were made to determine the effect of decreas- 
ing salinities on survival of Zhais embryos in capsules. It was found 
that the salinity could be dropped suddenly from 27 to 13 parts per 
thousand and allowed to remain there for several days without ill, 
effect. A sudden drop from 27 to 4 parts per thousand kills all em- 
bryos within 20 minutes. However, if the salinity is lowered slowly, 
it may be reduced from 27 to 3 parts per thousand before mortality 
begins. These experiments were made at temperatures between 26° 
and 381° C. 
No young 7'hais were taken in the field from the end of the spawn- 
ing season until October 26, at which time the average length of 
those taken was 21.1 mm. On December 15 the average length was 
26.9 mm. It is interesting to observe that the average length of 
young oysters eaten by young 7’hais, as of December 15, was 22.2 mm. 
Although young 7'ha?s prefer oysters they also consume mussels and 
barnacles. 
AUTONARCOSIS IN THE OYSTER AND ITS INDUSTRIAL APPLICATION 
It is well known that oysters in the shell can live out of water 
for several days, permitting their transplantation to selected growing 
areas or shipment to inland markets. Recent studies conducted by 
Dr. Prytherch, at the Beaufort laboratory, show that the ability 
of the oyster to survive outside of its natural environment is due 
to the fact that it puts itself into a state of suspended animation 
or narcosis soon after the shell is closed. In very young stages of 
Ostrea virginica, the functioning of many internal organs can be 
clearly seen through the transparent shell. Soon after shell closure 
there is complete cessation of heart action, blood circulation, ciliary 
movement, and a general inhibition of all metabolic activities, ac- 
companied by a rapid increase in the hydrogen-ion concentration 
of the liquor. 
Experiments have shown that the tissues of the oyster are narco- 
tized by carbon dioxide generated principally by the gills, and that 
this condition is due primarily to the rapid development of a high 
carbon dioxide tension within the shell rather than to an increased 
hydrogen-ion concentration. Carbonic acid is particularly suitable 
for conserving the energy and prolonging the hfe of the oyster 
outside of its natural environment, as it readily penetrates and 
leaves the tissues without producing injury or the noticeable after- 
effects which result from most narcotizing substances. 
In commercial operations approximately 60 percent of the oysters 
are shucked and washed before marketing. It was found that the 
meats are rarely killed by shucking and will survive washing in 
fresh water up to 3 minutes. If then placed in the usual airtight tin 
containers they will generate sufficient carbon dioxide to produce 
narcosis and reach the market alive and in as good condition as 
when shipped in the shell. Under these circumstances the oyster 
