200 
BULLETIN OF THE BUREAU OF FISHERIES 
Later on, Wells, in 1920 and in the following years, working under the auspices 
of the New York State Conservation Commission (1923-1927) developed a method 
based on the use of a high-speed centrifuge; briefly speaking, the method is as follows: 
Artificially fertilized eggs are allowed to stay in the containers and develop into 
larvae which are immediately transferred into 50-gallon stoneware jars. Once a day 
the content of the jar is passed through a high-speed centrifuge (De Laval multiple 
clarifier) and all the larvae, after being collected in the bowl of the centrifuge, are 
transferred into a new jar filled with fresh sea water. After the larvae attain a suffi- 
cient size to be retained by the fine wire screen (200 mesh to an inch) which was 
used during the changing of the water, they are kept in larger tanks where they 
finally set. 
In 1924 Prytherch reported the result of his experiments on artificial prop- 
agation of oyster larvae which had been carried out in 1923 at Milford, Conn. His 
method consisted in obtaining natural spawn from the oysters brought from the 
harbor and in keeping the oyster larvae in a system of tanks; the changing of water 
was accomplished by a slow filtration through the porous artificial stone known as 
filtros. When the larvae were about 10 days old, they could be held by means of 
fine screens of monel metal, which permitted a good flow of water. By this method 
Prytherch was able to produce several thousand seed oysters, which at the end of 
the summer were planted in Milford Harbor. 
The question of whether the methods of artificial propagation developed since 
1920 have reached such a perfection that they can be instrumental in rehabilitation of 
the industry, requires careful consideration. We read in the Annual Report of the 
Conservation Commission of the State of New York (1926, p. 125) that “as to the 
artificial propagation of oysters, the State feels that the problem has been solved.” 
Unfortunately, the data given in the reports of the New York Conservation Com- 
mission for the years 1923 to 1927 referring to the number of artificially propagated 
oysters, fail to support this optimistic view. The present annual production of seed 
oysters in Massachusetts, Rhode Island, Connecticut, and New York amounts, ac- 
cording to the data of the United States Bureau of Fisheries, to 586,443 bushels 
valued at $657,392, or $1.13 a bushel. The actual figure of production is several 
times higher, because seed oysters produced and replanted by the same company 
are not recorded by the statistics, which include only oysters bought or sold on the 
market. Every serious attempt to put artificial propagation on a commercial scale 
must take cognizance of the two main factors — the quantity of seed oysters required 
by the industry and the cost of production. If, under the present conditions, no 
large quantities of seed oysters can be raised artificially or should the cost of arti- 
ficial propagation be too high, then the problem is not solved. The difficulty only 
begins when one attempts to produce hundreds of thousands of bushels instead of a 
few thousand individuals. 
Present methods of artificial propagation are expensive; the reports of the New 
York Conservation Commission give no information as to the possible cost of pro- 
duction and fail to show the total number of oysters produced by Wells’s method. 
In the report of 1923 Wells states (p. 46) “that it has been impossible to determine 
accurately the yield of the operation. Altogether, approximately 10,000 were planted 
as set in the open waters. This represents, however, only a small portion of the total 
number of larvae developed in the jars.” From a practical point of view, the number 
of larvae raised in jars or tanks has very little significance; the real test of the method 
is in the production of seed oysters; and, as one can judge from the report of the 
