332 REPOET OF COMMISSIONER OF FISH AND FISHERIES. 



in the pond will be lower than tl in the open water, and under those circumstances 

 there will be an inflow of sea water into the pond through the diaphragm instead of 

 an outflow, as is the condition of the water level during ebb tide. Under such condi- 

 tions there will be four alternating periods during every twenty-four hours of inflow 

 and outflow, lasting, we will say, four hours each, not reckoning the nearly stationary 

 intervals between tides or during slack water. This almost constant partial renewal 

 of the water will unquestionably maintain the water inclosed in the pond or ponds 

 by means of diaphragms in a condition fitted to support oysters colonized therein, 

 provided its density is not too great or too slight, and if there is also some micro- 

 scopic vegetation present. 



It will be readily understood from the preceding description how it is intended 

 that the apparatus is to be operated. The figures also give a very good idea of how 

 the diaphragm and trunk are to be constructed, the first four figures being drawn 

 to a common scale of 1 inch to 3 feet.* 



The water iu the pond remained at about the same density and tem- 

 perature as that iu the open bay and soon developed a greater abun- 

 dance of food organisms, both plants and animals. Artificially fertilized 

 ova were placed in the pond at intervals during the spawning season, 

 and forty-six days after the beginning of the experiment young spat 

 from one- fourth to three-fourths of an inch long were found attached 

 to the bunches of shells which had been hung upon stakes to serve as 

 collectors. Great difficulty was experienced from sedimentation. The 

 experiment demonstrated that spat could be raised in ponds from 

 artificially fertilized eggs and that it would grow as rapidly as the spat 

 reared in the o] en bay. As the conditions are stated by Dr. Eyder, it 

 appears probable that equally good or better results might have been 

 attained with less labor by placing a quantity of spawning oysters in 

 the x^ond. 



Not only would there be a saving of labor in the direct use of the 

 spawning oysters, but there would also be no necessity for the sacrifice 

 of the parents, as must be done under the method of artificial fertiliza- 

 tion. The increase in the size of the spawners under the favorable 

 conditions of growth would probably go far toward the payment of 

 expenses. 



The method which promises the best results is that in which the eggs 

 are deposited in the pond within from three to five hours after fertili- 

 zation. There is apparently nothing to be gained in holding the eggs 

 a longer time, the chief gain of the culturist being not in the protection 

 of the embryo, but in the increase of the proportion of eggs fertilized. 



The method of fertilization used by Dr. Eyder was as follows : 



The method formerly used was to first learn the sex of a number of adult oysters 

 with the microscojie, then cut out the generative glands with their products and 

 chop up those of different sexes separately iu small dishes with sea water. This 

 system we may now say is barbarous, because it is crude. Large numbers of eggs are 

 destroyed by crushing, or are injured by the rough usage to which they are subjected, 

 and, besides, there is no assurance that the eggs or milt operated with are quite 

 mature. It is also troublesome to free the generative gland from fragments of the 

 liver, which help to pollute the water in the incubating vessels with putrescible 



*Bull. U. S. F. C. 1884, pp. 19, 21, 22, 23. 



