656 U. S. BUREAU OF FISHERIES 
an enormous task. Another thing with regard to artificial propagation is that 
it invariably succeeds when natural propagation succeeds and fails to produce 
results when results are needed most. 
In order to carry on the experiments with the collectors it was necessary 
that we have wider knowledge of oyster larve and their behavior. For in- 
stance, in Milford Harbor, and in experiments carried out in Long Island Sound 
over a period of several years, we were able to collect the oyster larve when 
they were 2 days old, but could not find any trace of them again until they 
were within a day or two of setting. They are quite active a few days before 
setting, so that we were able to find many of them in this stage of development. 
In 1925, when Milford Harbor had been stocked and when spawning was known 
to have occurred, attempts were made to collect larve so as to determine their 
size and relative abundance. We were unable to find any except the smallest 
straight-hinge larvee, and so we decided to take a sample of bottom mud or 
sand and see if we could find any trace of them there. In these samples we 
found quite a number of the larve in the intermediate stages of development, 
for which we had been searching for many years. 
It is evident that the oyster larve in Milford Harbor spend a great deal of 
time lying on the bottom, and, in that particular body of water, conditions are 
such as to influence their behavior in this respect. The important point is that 
it gives us some knowledge as to the behavior of the oyster larvee previous to 
the time of setting. 
In bodies of water where conditions are more quiet we found the oyster larvze 
throughout all stages swimming around in the water. In Milford Harbor the 
strong tidal currents make it necessary for them to protect themselves from 
being carried away, so they have developed this habit of settling to the bottom. 
To inerease our knowledge of currents in Long Island Sound, we released 500 
drift bottles. Some of the bottles made journeys of 50 miles in 5 to 12 days, 
and the majority moved great distances from places where they were placed 
originally. From the drift-bottle records it is obvious that if the oyster larvee 
did not adapt themselves in this way to combat the currents they would be 
earried far away from the spawning beds, and oyster-cultural work would be 
even more difficult than it is at present. 
Another great problem that has confronted us has been the peculiar attach- 
ment of the oyster spat in definite zones. In South Carolina and Georgia we 
found that setting occurred from low-water mark nearly to high-water mark; 
in Connecticut from the bottom of the channel to a point about 2 feet above 
low-water mark; and in South Bay, Long Island, from the bottom to the surface 
of the water. In South Carolina waters it was observed that the greatest 
intensity of the set occurred at a point midway between high and low water. 
Milford Harbor had its greatest intensity occurring at the level of low, slack 
water. 
From experiments at Milford Harbor it was found that the predominating 
factor that controlled the attachment of the oyster larve was the velocity of 
the tide. The time at which the greatest attachment occurred was when the 
tidal velocity was practically 0. The tides in Milford Harbor are such that 
the oyster larve are unable to attach after the tide has reached a point about 
2 feet above low water. At this point the tidal currents have developed a 
velocity of 10 centimeters per second, preventing the oyster larve from attach- 
ing themselves to any object. The type of tidal current in South Carolina and 
Georgia waters is different from that of Long Island Sound, with the result 
that the zone of attachment is different also. Of what significance is this 
knowledge to the industry? In South Carolina, though we found the oysters 
attached above low-water mark only, we knew that their absence below would 
not indicate necessarily that they could not live there, and so we took advan- 
tage of this condition by planting the seed oysters on beds below low-water 
mark, where successive generations are unable to attach and crowd them out. 
Doctor Galtsoff mentioned the effects of sperm on producing spawning in 
the oyster. In Milford Harbor water temperatures were high during the first 
part of July, but the oysters refused to spawn; so on July 15 I stripped some 
oysters and released the spawn over the beds with the result that the spawning 
occurred and spread over the entire spawning bed. This method was also 
earried out in Long Island Sound on the oyster grounds. The oysters were 
ripe and well filled with spawn and it was decided that no harm would be 
done by stripping them to induce the others to spawn. Five bushels were 
stripped and the product pumped down to the oyster bed. The oystermen that 
+ (BANG ot 
