28 CEYLON PKARL OYSTER REPORT. 



never had a glimpse of a shark dangerous to man. Several times the boatmen have 

 caught ' basking-sharks ' * of considerable size, but all were of a species that lives 

 almost entirely upon small fishes and mollusca." 



CONDITION OF SPAT ON THE PERI Y A PAAR IN 1904. 



" March 14th was devoted to an inspection of the Periya Paar, with the result that 

 an immense bed of oyster spatt was there discovered. The young oysters were 

 incredibly abundant, spread densely over an area fully 5 miles in length by from 

 1 mile to l miles in width. The age was under 3 months, so that they must have 

 been spawned not earlier than December of 1903, more probably towards the end of 

 the month. Alike on sandy and on rocky ground was this profusion seen, but on 

 the rock the numbers were notably greater. On the sandy stretches the oysters 

 formed bunches often of large size, the individuals attached in most cases to one 

 another, but generally having a nuclear fragment of small cultch which most frequently 

 was a cockle shell, a nullipore ball (Lithothamnion) or a small fragment of 'paar.' 

 The spinning mussel (Modiola barbata), 'Suran' as it is called by the Tamil divers, 

 was in places abundant, especially upon the sandy ground, but not sufficiently so 

 to constitute a grave danger to the bed. This discovery of spat paralleled in extent 

 and nature that made by Professor HERDMAN in February, 1902. when he estimated 

 approximately the numbers of the young oysters at 100,000,000,000, and which, it 

 will be remembered, had all disappeared when I next examined the bank in November 

 of the same year. 



" A very remarkable fact was that some of the largest of these young oysters when 

 last seen, 3rd April, had already developed gonads filled with reproductive products 

 fully formed and ready to be shed. The average size of these sexually mature 

 individuals was 25^ millims. X 26 millims. X 9 millims. The smallest was 

 24| millims. X 25 millims. X 8f millims. The extreme age of these cannot be more 

 than 3g- months, and we are fully warranted in considering that sexual maturity is 

 reached by the pearl oyster soon after the age of 3 months. Previous to this record, 

 the age of 6 months was the earliest at which reproduction had been observed." 



Sexual maturity at such a small size and early age, in itself remarkable, has a 

 practical bearing upon the replenishing of the banks from time to time a subject to 

 be treated of again. 



Principal Spawning Seasons. The gonads of this year's fish able oysters were nearly 

 all in a spent condition during February and March, and this taken in conjunction 

 with the presence of enormous multitudes of very young oysters so young indeed 

 that they could not have been set free earlier than the middle of the December 



* The sketch of one of these which Mr. HORNKLL has sent home has been identified by Mr. G. A. 

 BoULENOER as Stegostoma tigrinmn (GMEL.). 



t The term " spat " is used in these pajus in a wide sense to comprise all sizes of attached oysters 

 under the age of 4 months. 



