654 U. S. BUREAU OF FISHERIES 
ment gave 16,000 and 11,000, and 9,000 and 7,000, respectively. These results 
indicate that a great many bacteria are able to pass through the gills. 
The next important physiological question is the spawning of the oyster. 
Literature on the oyster contains many: descriptions of the spawning habits 
of the oyster, but no real study of the phenomenon has been made as yet. 
The experiments were performed last summer with the oysters attached to the 
kymograph and kept in the tank where temperature, oxygen content, and pH 
were kept constant. The results of the experiments show that both male and 
female oysters can be induced to spawn by increasing the temperature of 
water in which they are kept. The kymograph records show that the spawn- 
ing reactions of the male and female are different; in the first case the shell 
is kept open and the sperm flows in a continuous stream with the outgoing 
current of water; in the second case the rhythmical contractions of the 
adductor muscle cause the closing and opening of the shell. However, there 
is an additional factor that is responsible for the spawning of the female 
oyster. At a constant temperature the female can be induced to spawn by 
adding a small amount of sperm to the water. As the kymograph records show, 
the reaction lasts from 15 minutes to several hours, after which the oyster 
becomes insensitive to the subsequent addition of sperm. The sensitivity is 
restored, however, after two or three days. There is a certain minimum dose 
of Sperm that produces the reaction. Two or three doses, each of which is less 
than a minimum dose, produce no reaction, though the total amount of sperm 
added is larger than the minimum dose. The oyster becomes immune, how- 
ever, but comes back to normal condition after two or three days. 
The results of this experiment have several practical applications: First, it 
shows that in order to obtain a successful spawning on the oyster grounds the 
oysters should lie rather densely, but not be scattered over the bottom; second, 
that when the temperature of water is low and the oysters do not spawn, they 
can be induced to spawn by adding sperm to the water. The latter experiment 
was tried in Milford by Mr. Prytherch and was successful. 
Leaving the field of physiological research, we have to turn to some other 
work, namely, the study of the conditions under which the oyster grows. 
Investigations have been carried out during the last two years on Cape Cod, 
Long Island Sound, and the coastal waters of South Carolina, Georgia, and 
Texas; at present we are conducting investigations in Mississippi Sound, Miss., 
and Pamlico Sound, N. C. The purpose of these investigations, made at 
the request of the State authorities or representatives of the industry, is 
to answer the practical questions: How and where to plant oysters and how 
to utilize the natural oyster reefs and beds; how to grow better oysters? I am 
not going into the details of all the phases of this work, but If wish to make 
a general review of the conditions existing in the waters of the North Atlantic, 
South Atlantic, and the Gulf of Mexico. 
The chief problem in the North Atlantic is the production of seed oysters. 
Set is getting scarce, and the production of a good set is the key to success 
in oyster culture. Extensive investigations and experiments on the behavior 
of oyster larvee were made in northern waters. Last year artificial spat collec- 
tors were developed and tested in Great South Bay, Milford, Wareham, and 
Wellfleet. Instead of scattering oyster shells over the bottom, they were put 
into erates built of lath and planted over the various bottoms. Mr. Prytherch 
will describe the results of this experiment; it will suffice to tell at present 
that by this method the productivity of a given area of sea bottom can be 
increased from seven to ten times; and, besides, bottoms not suitable for ordi- 
nary planting, as, for instance, mud flats or sandy bars, can be utilized. In 
the southern waters the setting is so abundant that every object is covered 
with spat. This creates overcrowded conditions and results in the formation 
of oyster reefs or beds consisting in so-called “coon” oysters of a very little 
market value. Fortunately, in these waters setting seldom occurs below low- 
water mark, so that oysters planted there are not crowded out by successive 
generations and develop into a well-shaped product. The practical method of 
oyster culture in these waters is to obtain seed oysters on brush, then to trans- 
plant them into deep water. This method has been tried on a small scale in 
Georgia and has proved successful. 
The study of the enemies of the oyster is of great importance. Out of 
many organisms that prey on oysters, the drill is the most dangerous and 
the most difficult one to combat. In certain localities, over 70 per cent of 
the oysters are destroyed by the drill. So far we have no efficient method 
