PROGRESS IN BIOLOGICAL INQUIRIES, 1936 35 
the muscles, gills, and the rest of the tissues showed a manganese con- 
tent varying from 5 to 38 mg per kilo. A study of the localization. 
of other metals in various organs revealed the interesting fact that 
the gills and mantle accumulate much larger quantities of metals 
than other parts of the oyster. In one experiment the mantle and. 
gills were found to contain respectively 22,000 and 19,400 mg of zine 
per kilo as compared with 14,300 mg in the ween mass, and only 
1,590 in the muscles. 
The possibility of increasing the iron content of the northern oyster 
which, as has been established | by the work of Coulson, is lower in this 
metal than the oysters from the South Atlantic States, has been tested 
in the laboratory and in outdoor tanks at Milford. Oysters kept in 
the laboratory and fed various iron salts showed only very slight 
increase in iron content in spite of the fact that they easily ingested the 
suspended iron oxide particles. The experimental work at Milford 
was undertaken with the cooperation of the Department of Physiolog- 
ical Chemistry of Yale University, which granted laboratory facilities 
for the chemical analyses. Two large concrete outdoor tanks, in which 
the water could be changed by the tides whenever desirable, were 
selected in order to keep the oysters in as nearly natural a condition 
as possible. Iron in the form of rusty nails was added to one tank 
and the other kept normal as a control. Initial samples for iron 
analysis were taken of oyster meats and sea water before the addition 
of any iron, and thereafter samples were taken from each tank at 
regular intervals. ‘The nails added to the tank became quite rusty 
but apparently the rust formed is insoluble in sea water for no increase 
in soluble iron could be detected in 6 weeks. The experiment is being 
continued with iron added in the form of copperas, a cheap technical 
iron salt, and the indications are that this method will be successful. 
PROPAGATION OF OYSTERS 
Problems of the propagation of oysters were studied at Woods Hole 
where Dr. Galtsoff began an experiment on sex reversal in adult oysters 
and at the Milford Laboratory where Dr. V. L. Loosanoff followed the 
development of gonads in adult oysters of Long Island Sound. 
The problem of sex reversal in adult American oysters is little, 
understood. An experiment was therefore undertaken in an attempt 
to determine the factors involved in this phenomenon. To avoid the 
possible effect of injury, the sex of 202 adult oysters was determined 
by stimulating spawning, examining the dischar ged material and ob- 
taining a kymogr aph record of the : spawning reaction. Each oyster 
was then marked by cutting a number in its shell. Early in September 
all the oysters thus treated were brought to Milford and placed in 
the experimental tanks in five groups: Females only; males only; 
males and females in the ratio 2 to 10; and two groups containing 
both sexes in equal proportions. The purpose of the experiment was 
to determine whether the association of individuals of different sexes is 
one of the factors involved in sex reversal, as has been claimed by 
some investigators. 
For the study of gonad development samples of oysters were col- 
lected from Charles Island oyster beds at biweekly intervals through- 
out the year. After the completion of spawning, the gonad follicles 
of oysters begin to shrink very rapidly, at the end of August occupy- 
