FIFTEENTH ANNUAL MEETING. 27 



holds it at all times. It will be noticed by the record given 

 below, that the water in this pond, which has a depth of two to 

 six feet, was warmer as a rule, than that in the wooden tank in 

 the shade of the building, and it was in the pond that our great- 

 est success was made. 



We obtained oysters at the spawning season from the oyster- 

 men here, and these were opened, and all whose appearance 

 denoted ripeness were selected and placed one side. The sign 

 of ripeness was the peculiar fulness and milky appearance of 

 the ovaries and spermaries which is readily seen by any person 

 who is at all familiar with them. The oysters then, lying on 

 one shell, were taken and the mantle and gills trimmed off 

 with small sharp scissors ; pressure was then applied with the 

 scissors to the ovaries and the exuding drop was placed upon a 

 glass slide under the microscope, where the eggs can readily be 

 distinguished from the milt of the male, after a person has once 

 had the difference pointed out to him. 



The male oysters were separated from the female, so that we 

 could see what proportion we had of each. Sometimes we 

 would lack the male element and consequently could get no 

 impregnation. At other times there was a fair amount of both 

 sexes. The eggs were stripped from the female by pressure, 

 and then the male was treated in the same manner, taking both 

 the eggs and milt in an ordinary milk pan and adding water 

 gradually. In a short time a drop of this water placed under 

 the microscope would be seen swarming with the spat in the 

 swimming stage of its existence, and then they were placed in 

 the tank or in the pond. The bottom of the tank was covered 

 with gravel, and scollop shells were suspended on strings across 

 it. The current was very light and the spat seemed to sink and 

 catch upon the gravel, for we caught none upon the hanging 

 shells in this water. Toward the last of August, the tank was 

 examined and the few oysters adhering to the gravel were 

 removed and placed in the salt-water pond. The success in this 

 wooden tank was not as complete as the experiment in the pond, 

 and but few oysters were got from it. 



During July and August, while the record was kept, tiie 

 variations in temperature were very slight, while the density of 



