PROGRESS IN BIOLOGICAL INQUIRIES, 1926 653 
and other natural-history features are being made as opportunity offers. The 
abundance of the set on any bed determines the amount of digging that it 
will support, and efforts are being made to determine the success of each 
spawning. ; 
The work has been carried on continuously since 1923. Special attention 
has been given to the beds most in need of protection. The ring method of 
age determination has been found to apply to this form. By the use of it, 
the course of growth for the more important beds and the age and size -of 
sexual maturity have been determined. The relation of water temperature 
to the time of spawning has been studied on the Washington beach, as records 
from Alaska are difficult to obtain. 
OYSTERS 
GENERAL REVIEW—OYSTER SURVEYS AND EXPERIMENTAL PHYSIOLOGY 
By Dr. P. 8. GALTSOFF 
The purpose of the oyster investigations is to discover the method by which 
the production of oysters can be increased and better oysters can be pro- 
duced. It sounds like a very simple problem; but, as you know, those prob- 
lems that appear to be the simplest are often the most difficult for scientists. 
The solution of the problem requires a perfect knowledge of the organism and 
of the conditions under which it propagates itself and grows. This involves 
a study of the physiology of the organism and of the ecological conditions 
existing in the sounds, bays, and other bodies of water where the oyster grows 
in abundanee. Thus, the investigation of the oyster fishery covers a great 
variety of physiological and hydrobiological problems. Geographically, this 
work extends from Cape Cod to the Gulf of Mexico. 
I shall begin my review with the description of some physiological experi- 
ments that have been carried out during the past summer at Woods Hole. 
The first question that appears to be a very important one is that of the 
feeding of the oyster. Many attempts have been made by various investigators 
to determine the manner of feeding, but no accurate method has been evolved as 
yet. At the present stage of science no real progress can be expected unless 
a quantitative method is developed. We know, in a general way, that the 
oyster feeds on plankton carried in by the current produced by the gills. 
The first thing in this problem is to find out how much water is carried in 
and how many organisms are caught by the gills. The feeding of the oyster 
consists in three distinct phenomena: (1) Opening and closing of the shell, 
caused by the contraction of the adductor muscle; (2) production of currents 
by the ciliary epithelium; and (3) swallowing of the microorganisms caught 
by the gills. Only the two first phenomena so far have been studied. 
The closing and opening of the shell were studied with a recording apparatus, 
which registers automatically every motion of the shell. The records show 
that on an average the oyster keeps its shell open for about 20 hours a day. 
To study the currents produced by the gill epithelium a new method has 
been developed which enables us to determine accurately the amount of water 
that has passed through the oyster and to measure the pressure developed 
inside the gill cavity. It is also possible to collect the water that has passed 
through the gills and analyze it. Inasmuch as this method has been described 
in Science, I shall not enter into the details. It reaches its maximum (about 
4 liters per hour) at 25° C. and slows down with the decrease of temperature 
Below 7° C. no current is produced, though the cilia are still beating. This is 
entirely in accordance with the theory of hibernation developed by the bae: 
teriologists who found that in winter, oysters taken from the polluted beds show 
a very low Bacteriwm coli score, while in summer the B. coli score of oysters 
taken from the same beds is very high. 
By using my method, the water discharged from the gills can be collected 
and analyzed easily. Counting the microplankton in the tank water and in the 
discharged water, I found that more than 99.5 per cent of diatoms and dino- 
flagellates are caught by the gills. Water, after having passed the gills, con- 
tains almost nothing but mucus. With the cooperation of Doctor Pease’s labo- 
ratory, I was able to make a few experiments to determine whether the bacteria 
are caught by the gills or if they pass through them freely. The following 
results were obtained: Water containing 27,000 B. ccli per cubic centimeter 
contained, after passing through, 24,000 per cubic centimeter; another experi- 
