132 CEYLON PEAKL OYSTER REPORT. 



May 20th. Another of the usual nightly moves. This time a distance of 3f inches 

 had been covered, 4 strands being formed at the new anchorage this was the 

 seventh journey within 14 days. From this date to the time when replaced in the 

 cage at the harbour buoy, 10 days later, no further movements took place the animal 

 at last appearing contented with its position. 



Individual No. 2 was of the same age as No. 1, and had a similar history. On 

 May 9th it was placed in No. 1 tank, and 5-J- days later was found anchored by a 

 stout, pale-yellow tinted byssal strand to the outside of a glass vessel, against which 

 it rested. Close by lay its old byssal bundle, with white sloughed-off root. The 

 attachment had been made (as usual) during the night. Pearl oysters are always 

 most active after sunset. 



May 16th, 8 a.m. Three new byssal strands were formed during the night. The 

 older one had now assumed a dark-green colour. 



May 17th, 8.30 a.m. Five new strands have been made since the preceding sunset. 



May 18th. This morning this oyster was removed to another tank, and the byssal 

 attachment was forcibly torn. It was laid under the inflow-pipe, and within 

 5 minutes thereafter the foot was protruded, feeling slowly all around. Then, after 

 one or two momentary withdrawals into the shell, the foot was placed in position, 

 the anterior part being pressed sucker-like against the tank side. In 4i minutes the 

 foot withdrew, showing a new byssal thread anchoring the oyster to the tank. The 

 old byssus was thrown out in the course of the next hour. During the rest of the 

 day 4 other strands were formed, and 16 more in the course of the ensuing two days. 



May 21.vf, 8 A.M. During the night this oyster had cast off the byssus, travelled 

 2 inches, and then made a re-attachment by 14 new byssal strands. 



May 2ith showed another night march to have taken place. The distance travelled 

 was 1 inch. The new byssus, the fourth since being brought into the aquarium, 

 consisted of 3 strands. The next night again showed another move of 2\ inches, 

 with re-attachment by 9 new stout silvery fibres. After this it made no further 

 change, remaining affixed to the bottom of the tank till July 3rd, when it was 

 removed. The length of its fully extended foot was 1{ inches from the tip to the 

 centre of the mouth of the byssal gland. 



The other oysters of this batch took from 5 to 7 days to form their first re-attach- 

 ment after being brought in from the cages in the harbour. Subsecpiently, when the 

 water-circulation in the aquarium was improved, re-attachment of freshly introduced 

 individuals took place much more quickly. Thus, of a number placed in the tanks 

 on June 1st, at 12.30 p.m., one threw off the old byssus, crawled 2 inches, and 

 re-attached, all within 2 hours after being brought in. At 6.30 p.m. (sunset) the 

 same day all the remainder became active the first sign in nearly every case being 

 the casting away of the old byssal root. A few crawled a short distance, but the 

 majority merely protruded the foot, feeling round, and then at once began the work 

 of forming new cables. At 8.30 p.m., the greater number had made new attachments,. 



